Hybrid analog/digital beam forming rain fade mitigation

ABSTRACT

Fade conditions are determined for each gateway in gateway clusters of a set of gateway clusters. A proper subset of the gateway clusters is selected based on the fade conditions determined for each gateway. A beam plan is determined based on the proper subset of the gateway clusters. The beam plan is executed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/571,574, filed Oct. 12, 2017, the contents of which is incorporatedby reference in its entirety.

TECHNICAL FIELD

The following disclosure relates generally to a hybrid analog/digitalbeamforming communications system.

BACKGROUND

Some communications systems, e.g., a satellite communications system,provide multiple communication beams that connect diverse terrestrialregions. In some cases, a target area is covered using analogcommunications beams. Alternatively, in some cases, a target area iscovered using digital communications beams.

SUMMARY

The following disclosure describes a communications system for hybridanalog/digital beamforming to generate a set of communication beams(also referred to as “beams”) to cover a target area. The systemincludes a beamforming apparatus for generating hybrid analog/digitalbeams, where beamforming refers to techniques to form beams to establishcommunications channels. In some implementations, the beamformingapparatus is a spacecraft, e.g., a satellite, a drone, an airplane, oran aerial platform. In other implementations, the beamforming apparatusis a ground-based apparatus, e.g., an antenna tower. The followingsections describe the hybrid analog/digital beamforming in the contextof a satellite. However, the techniques are also applicable to otherbeamforming apparatus, e.g., other forms of space-based beamformingdevices or terrestrial beamforming structures.

In some implementations, a satellite that performs hybrid analog/digitalbeamforming includes multiple antenna radiating elements (also known as“feeds”) and associated phase shifters for forming analog beams. Thesatellite includes processing circuitry, comprising one or morebeamformer processors, that control the feeds to form the analog beams.The feeds are divided into groups among hardware structures called“panels,” also referred to as analog beamformers. The processingcircuitry controls the panels to form one or more analog beams perpanel, with the analog beams from some or all the panels providingcoverage in a region in the target area, generating a cluster. Thebeamformer processors in the processing circuitry also form digitalbeams using digital beamforming coefficients stored in tables. Theprocessing circuitry forms one or more digital beams in the cluster byphase and gain combining the analog beams in the cluster. The hybridanalog/digital beams, e.g., digital beams that are generated bycombining the analog beams in a cluster, are also referred to as hybridbeams.

Hybrid beams are accordingly digital beams that are generated in ahierarchical manner—first by forming analog beams, and then by combiningthe analog beams to form the digital beams that correspond to the hybridbeams. In contrast, pure digital beams are formed by directly combiningthe phase, delay, or amplitude (or gain) of the feeds using digitalcoefficients—there is no intermediate formation of analog beams. Puredigital beams can be created in any region. In contrast, in hybridbeamforming, the digital beamformers in the spacecraft are constrainedto create the hybrid beams, i.e., the digital beams, within the coverageareas of the underlying analog beams. The analog beamformers combine theanalog beams to provide the contours of the coverage areas in which thedigital beams are generated.

The satellite in the communications system divides a target coveragearea into multiple regions. The processing circuitry in the satelliteprovides, in a region, analog beams formed by one or more panels tocreate a cluster, and generates one or more digital beams for thecluster by combining the corresponding analog beams, as noted above. Insome implementations, the footprints of the analog beams overlap to somedegree, e.g., either partially or completely. In such cases, digitalbeams are formed by combining the overlapping analog beams. In someimplementations, the footprints of at least some of the analog beams arenon-overlapping. In such cases, at least some digital beams are formedby combining separate groups of the analog beams, which can includeoverlapping analog beams.

After forming the hybrid beams in a region, the processing circuitryrepeats the process in a neighboring region, until all the regions areaddressed, thereby covering the target area with the hybrid beams. Theprocessing circuitry arranges the hybrid beams in a cluster in rows andcolumns. In some implementations, the processing circuitry horizontallyshifts some rows, or vertically shift some columns, or both, to conformto the boundaries of the cluster. Additionally or alternatively, theprocessing circuitry stretches or contracts hybrid beams in some rows,or some columns, or both, to conform to the boundaries of the cluster.In some implementations, the processing circuitry horizontally shiftssome rows, or vertically shift some columns, or both, in a cluster suchthat the rows and columns of hybrid beams in the cluster are adjacent tothe rows and columns of hybrid beams in a neighboring cluster, for nogap in coverage.

In attempting to satisfy communication requirements, the communicationssystem may also attempt to mitigate fade conditions. Fade conditions areconditions that cause signals between the satellite and the ground tofade. For example, if it is raining at a particular location, a signalthat normally may be received at 50 dBW may be attenuated by −5 dBW bythe rain so that it is only received at 45 dBW. The satellitecommunications system may attempt to mitigate for fade conditions tothereby prevent degradation of communications service quality that canoccur as a result of the faded signals. For example, attenuation of asignal by rain may reduce the data capacity available through the signalas the signal may experience more interference.

To ensure the satisfaction of quality of service when there are changingfade conditions, the satellite communications system may attempt tomitigate fade conditions by permanently increasing the power of alltransmitted signals. However, this approach may increase thetransmission power capacity requirements of the satellite communicationssystem and waste power when no fade conditions are present. Instead ofpermanently increasing the power of all transmitted signals, thesatellite communications system may attempt to dynamically mitigate fadeconditions.

The satellite communications system may dynamically mitigate fadeconditions by selecting different gateway clusters to use among multiplegateway clusters, where each gateway cluster includes multiple gatewayslocated at different geographical locations and selection is based onestimating fade conditions at the gateways in the gateway clusters. Eachof the gateways in each gateway cluster may be covered by an analog beamand different digital beams. When the satellite communications systemselects to start using a spare gateway cluster due to fade conditions,the analog beams that covered the gateways in the gateway cluster nolonger being used are moved to cover the gateways in the spare gatewaycluster and relative locations of the digital beams within the gatewaycluster no long being used are realigned to match the geographicallocations of the gateways in the spare gateway cluster.

By dynamically mitigating for fade conditions, the satellitecommunications system may permit the use of satellites that have a lowertotal power output capacity and may reduce the power usage of thesatellites, among other advantages.

One innovative aspect of the subject matter described in thisspecification is embodied in a method that includes the actions ofdetermining fade conditions for each gateway in gateway clusters of aset of gateway clusters, selecting a proper subset of the gatewayclusters based on the fade conditions determined for each gateway,determining a beam plan based on the proper subset of the gatewayclusters, and executing the beam plan.

The foregoing and other embodiments can each optionally include one ormore of the following features, alone or in combination. For instance,in some aspects the gateways in each gateway cluster are operable toform an analog beam with a satellite where at least some of the analogbeams in each gateway cluster at least partially overlap and combine toform a digital beam. In certain aspects, selecting a proper subset ofthe gateway clusters based on the fade conditions determined for eachgateway includes determining an aggregate data capacity for each of thegateway clusters based on the fade conditions and selecting the gatewayclusters with aggregate data capacities that are the highest out of theset of gateway clusters. In some implementations, selecting a propersubset of the gateway clusters based on the fade conditions determinedfor each gateway includes determining a number of gateways thatsatisfies a fade threshold for each gateway cluster and selecting thegateway clusters with the most number of gateways in the gateway clusterthat satisfy the fade threshold.

In certain aspects, selecting a proper subset of the gateway clustersbased on the fade conditions determined for each gateway includes notselecting a gateway cluster in the set of gateway clusters for inclusionin the proper subset, where the gateway cluster that is not selected iscurrently being used to transmit data with a satellite and selecting agateway cluster in the set of gateway clusters for inclusion in theproper subset, where the gateway cluster that is selected is notcurrently being used to transmit data with a satellite. In some aspects,determining fade conditions for each gateway in gateway clusters of aset of gateway clusters includes determining a strength of signalsbetween each gateway and the satellite and determining the fadeconditions from the strength of the signals. In some implementations,determining a beam plan based on the proper subset of the gatewayclusters includes determining beamforming coefficients for each of thegateways in the proper subset of the gateway clusters based on thegateways in the proper subset of the gateway clusters.

In certain aspects, executing the beam plan includes providing, from thesatellite the beam plan to the gateways. In some aspects selecting aproper subset of the gateway clusters based on the fade conditionsdetermined for each gateway is performed by a satellite. In someimplementations, selecting a proper subset of the gateway clusters basedon the fade conditions determined for each gateway is performed by acentral operations center.

Implementations of the above techniques include methods, systems andnon-transitory machine-readable media. One such method performs theabove-described actions. One such non-transitory machine-readable mediumstores instructions that are executable by one or more processors andthat, when executed, are configured to cause the one or more processorsto perform the above-described actions. One such system comprises one ormore spacecraft, such as one or more satellites, or ground-basedbeamforming apparatus, such as one or more antenna towers, each of whichincludes one or more processors and instructions stored inmachine-readable media that, when executed by the one or moreprocessors, are configured to cause the one or more processors toperform one or more of the above-described actions.

The details of one or more disclosed implementations are set forth inthe accompanying drawings and the description below. Other features,aspects, and advantages will become apparent from the description, thedrawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary communications system that is used forhybrid beamforming.

FIG. 2 illustrates an example of a configuration of feeds on aspacecraft for hybrid beamforming.

FIG. 3 illustrates an example of a hybrid beamformer processingcircuitry in a spacecraft for generating hybrid beams.

FIGS. 4A and 4B present comparative illustrations of coverage providedrespectively by analog and hybrid beams in a target area on the Earth'ssurface.

FIG. 5 presents a comparative illustration of examples of coverage areasprovided by a pure analog beam and overlapping analog beams formed usinga hybrid beamformer.

FIG. 6 illustrates an example of hybrid beamforming to fully cover anon-circular shaped region.

FIGS. 7A and 7B illustrate examples of different cluster shapes that canbe formed using hybrid beamforming.

FIG. 8 illustrates an example of a process for forming hybrid beams.

FIGS. 8A and 8B illustrate examples of analog only hopping andanalog/digital hopping.

FIG. 9 shows an example use case where type 1 beams are used in clustersin a non-uniform laydown.

FIGS. 10A and 10B illustrate examples of dynamic resource transfer inhybrid beamforming to provide communications coverage to multipleregions.

FIG. 11 illustrates an example of a process for resource transfer inhybrid beamforming.

FIGS. 12A-12D illustrate examples of coverage flexibility provided by aspacecraft using hybrid beamforming.

FIG. 13 illustrates an example of a group of clusters shiftedhorizontally, or vertically, or both, to cover a target area.

FIG. 13A illustrates a graphical example of signal spread of co-channelhybrid beams and corresponding side lobes.

FIGS. 14A-14E illustrate an example of covering regions in a target areaby hybrid beamforming using groups of clusters.

FIGS. 15A-15C illustrate an example of sharing frequency spectrumbetween adjacent clusters in hybrid beamforming.

FIGS. 16A-16C provide comparative examples of communications coverageusing different cluster frequencies and shared cluster frequencies.

FIG. 17 illustrates an example of a process for providing communicationscoverage to a plurality of regions a target area using hybridbeamforming.

FIG. 18 illustrates an example of hybrid beamforming rain fademitigation.

FIG. 19 illustrates an example of a process for hybrid beamforming rainfade mitigation.

Like reference symbols in different figures indicate like elements.

DETAILED DESCRIPTION

In a communications system, e.g., a satellite communications system, asatellite can transmit signals to or receive signals from terrestrialdevices. For example, the satellite may receive a signal from a gateway,e.g., a ground station that communicates with the satellite and with aterrestrial network, and then broadcast the signal to one or more groundterminals, e.g., satellite dishes or antennas along with their connecteddevices in customer locations. In some cases, the satellite usesmultiple feeds, in, for example, a phased array antenna or as part of areflector antenna, to form one or more analog beams for communicatingwith terrestrial devices.

A radiating element or feed refers to a resonating structure that isdesigned to transmit or receive electromagnetic energy in a frequencyband (e.g., a microwave frequency band). A beam can be specified by aset of real or complex beam coefficients applied across the feeds of asatellite for analog beamforming, or to digital signals for digitalbeamforming. The beam coefficients may be determined based on satisfyinga required minimum average power over a region covered by the beam.

Beamforming can be accomplished onboard a satellite by constructing abeamforming network behind the feed array using one or more beamformerprocessors on board the satellite. A beamformer processor, whichincludes dedicated integrated circuit (IC) chips, computes coefficientsfor each intended beam, which include analog coefficients for analogbeams and digital coefficients for digital beams. For each feed, theprocessor applies the corresponding beam coefficient to a signal that istransmitted by the feed. The processor sends the signal to the feedthrough a high power amplifier (HPA) connected to the feed. In thismanner, the processor applies the computed beam coefficients to thefeeds to generate the desired beams for transmission of signals toterrestrial coverage regions.

In an analog beamforming satellite, a signal stream is divided amongeach of the feeds. The one or more beamformer processors form analogbeams by adjusting the relative phase and/or gain (or amplitude) of eachsignal path routed to each feed to thereby enable the energy radiated byeach transmitting feed to be coherently combined to create a beampattern composed of one or more beams. The same approach can also beused in the receive direction where the received signals from eachreceiving feed are coherently combined to create the beam pattern. Toform an analog beam, each feed uses a phase shifter. A feed can formmultiple analog beams with multiple phase shifters, requiring adifferent phase shifter for each analog beam.

The number of analog beams formed by a satellite depends on variousfactors, including the number of feeds and the number of phase shiftersper feed. Since every beam requires one phase shifter per feed, thehardware needed to generate a large number of analog beams (e.g., in theorder of hundreds or thousands) can become prohibitively high—e.g. interms of increased weight of the satellite, higher cost, or highercomplexity. Accordingly, the number of analog beams that can be formedby a satellite is often limited due to hardware constraints.

Digital beamforming, which is not limited by phase shifter constraints,can be used to create a large number of digital beams. However, togenerate digital beams, a satellite uses analog-to-digital (A/D) anddigital-to-analog (D/A) converters for each feed to convert associatedsignals into the digital domain. The satellite performs A/D conversionof the analog signal streams for the feeds to the digital domain, anduses the beamformer processor for combining the phase and gain of thedigital signals, relying on table lookup of digital beam coefficientsthat are stored in memory. Then digital signals are then converted backto analog using D/A conversion, and these are transmitted as separatesignals.

Although digital beamforming does not use phase shifters, since an A/Dconverter and a D/A converter is used for every single feed, thisintroduces a significant amount of hardware circuitry, e.g., wires goinginto a beamformer processor and going out of the processor to connectthe feeds. The hardware needs for digital beamforming to support a largenumber of feeds (e.g., in the order of hundreds or thousands) cantherefore also become prohibitively high—e.g. in terms of increasedweight of the satellite, higher cost, or higher complexity.

In some implementations, hybrid analog/digital beamforming, whichcombines analog beamforming with digital beamforming and isinterchangeably also referred to as hybrid beamforming, is used tosupport both a large number of feeds and a large number of beams, whileovercoming the constraints associated individually with analog ordigital beamforming for achieving these objectives. As described ingreater detail in the following sections, hybrid beamforming allowsanalog beamformer hardware (e.g., panels) to support a large number ofelements and digital beamformer processing circuitry to create a largenumber of beams. In doing so, with the same analog and digitalbeamforming hardware, hybrid beamforming provides a multiplicativeincrease in bandwidth and coverage area and higher edge of coverage(EOC) gains in the beams, compared to using analog beamforming ordigital beamforming individually.

Hybrid beamforming further allows customizing the beam footprints toprovide coverage for regions of various shapes and sizes. Digital beamsare iteratively generated in neighboring regions and adjusted in variousdirections relative to one another to provide complete coverage of atarget area comprising the regions, while maximizing the communicationscapacity in the target area.

FIG. 1 illustrates an exemplary communications system 100 that is usedfor hybrid beamforming. The communications system 100 includes asatellite 105 connected through satellite channels to gateways 110 and125, and ground terminals 120 a, 120 b, 120 c and 120 d, which arelocated on a planetary surface, e.g., the surface of the Earth. Althoughthe illustrated example of communications system 100 shows one satelliteand a limited number of gateways and ground terminals, variousimplementations can include different numbers of satellites, gatewaysand ground terminals without loss of generality. The following sectionsdescribe the planetary surface with respect to the Earth's surface.However, the techniques described are also applicable to other planetarysurfaces.

The satellite 105 transmits data to, and receives data, from thegateways 110, 125, and ground terminals 120 a, 120 b, 120 c and 120 d.Gateway 125 and ground terminals 120 a and 120 b are within aterrestrial region 130 a that is covered by a formed beam. Groundterminals 120 c and 120 d are within a terrestrial region 130 b that iscovered by another formed beam. That is, gateway 125 and groundterminals 120 a and 120 b are located within the geographic extentcovered by beam 130 a, while ground terminals 120 c and 120 d arelocated within the geographic extent covered by beam 130 b. The gateways110 and 125 are terrestrially connected to each other and to aterrestrial network 135 through communications link 140.

The satellite 105 can be located at a low earth orbit (LEO), a mediumearth orbit (MEO), or a geostationary orbit (GEO) location defined by alongitude. The satellite 105 interconnects the gateway 110, the gateway125 and the ground terminals 120 a, 120 b in beam 130 a, and the groundterminals 120 c, 120 d in beam 130 b, through satellite communicationschannels.

The satellite 105 includes multiple antenna radiating elements or feedsto form beams for transmission of information between the satellite 105and the gateways or ground terminals. The satellite 105 includes one ormore beamformer processors to process active signal streams forbeamforming. In some implementations, the satellite 105 also includesmultiple HPAs that receive the active signal streams from the beamformerprocessor, and forwards the signal streams with amplification to feedsthat are connected to the HPAs. The feeds transmit signals to or receivesignals from the gateways 110, 125 and the ground terminals 120 a-120 dusing the formed beams. A beam can encompass one or more gateways (e.g.,beam 130 a) within its coverage area, or a beam can encompass zerogateways (e.g., 130 b).

The beams 130 a and 130 b are hybrid analog/digital beams formed by thesatellite 105. The beams 130 a or 130 b, or both, are digital beams thatare generated by a digital beamformer on board the satellite bycombining analog beams generated panels. The digital beams 130 a or 130b, or both, are therefore hybrid beams formed within a cluster coveragearea of the analog beams. While only two hybrid beams 130 a and 130 bare shown, more than two beams can be active at a time in variousimplementations, and any number of ground terminals can be distributedamongst a plurality of beam coverage areas. The number of hybrid beamsthat can be simultaneously active depends on the number of panels on thesatellite used for generating analog beams, within the coverage area ofwhich the digital beams are created. As described in greater detailbelow, in some implementations, the number of hybrid beams can rangebetween tens to the order of thousands.

In this context, in some implementations, a panel is a hardwarestructure that provides a surface on which the constituent feeds of thepanel are positioned. Each panel can re-orient (e.g., tilt or move) theconstituent feeds relative to other panels. In some implementations, apanel is a radiating antenna structure that can form one or moresteerable analog beams. A panel is also referred to interchangeably asan analog beamformer, as noted previously.

The following sections describe configurations of the satellite 105 thatincludes processing circuitry with one or more one or more onboardbeamformer processors that control the analog beamformer panels togenerate analog beams, and perform digital beamforming on the analogbeams. In some implementations, the satellite 105 includes separateprocessors for analog beamforming and digital beamforming. In cases withmultiple analog or digital beamformer processors, the satellite includeslogic to operate the processors simultaneously for beamforming withsynchronization between signals processed by the different processors.As an illustrative example, in some cases, the satellite 105 includestwo digital beamformer processors. Each processor supports K panels (Kis an integer and K=5, 8, 10, 12, 15, 16, 20, 24, etc.), with each panelconfigured to generate up to Y analog beams (Y is an integer and Y=5, 8,10, 12, 15, 16, 20, 24, etc.). Each processor includes/input ports (I isan integer and I=32, 64, 128, etc.) and O output ports (O is an integerand O=32, 64, 128, etc.), with 2.5 Gigahertz (GHz) bandwidth (or anyother suitable bandwidth) per port. Each processor further supports 12.5Megahertz (MHz) channelization×N (for any integer N>0), with full meshrouting within a processor. In some implementations, the satellite 105includes one beamformer processor with a configuration similar to thatdescribed above.

The hybrid beamforming can be accomplished by space-based beamforming,i.e., on board the satellite, or ground-based beamforming (GBBF), e.g.,using a system on Earth, or using a system that combines bothspace-based beamforming and GBBF. In space-based beamforming, thesatellite 105 creates both analog beams using analog beamformers anddigital beams using digital beamformer processors on board thesatellite. In a GBBF system, the analog and digital beam coefficientsare computed by one or more processing systems on the ground. In someimplementations, the GBBF system creates the beams by applying thecoefficients to the signals, and then sends beams to the satellite fortransmission by forwarding through HPAs to the feeds. In otherimplementations, the GBBF system sends the coefficients to a beamformerprocessor onboard the satellite. The beamformer processor applies thecoefficients to the active signal streams and control the HPAs and feedsfor creating the beams.

In a combined system, the satellite 105 creates analog beams on boardthe satellite, while GBBF computes digital beam coefficients using oneor more processing systems on the ground. The GBBF system creates thedigital beams using the digital coefficients, and sends the digitalbeams to the satellite. Alternatively, the GBBF system sends the digitalcoefficients to the satellite, which uses one or more digital beamformerprocessors to create the digital beams within the coverage areas of theanalog beams.

In some implementations, the satellite 105 includes multiple reflectingdishes for reflecting or redirecting the energy used to form the beams.A reflecting dish may be configured to redirect the beam formed by agiven set of feeds. The analog beams can be formed by the satelliteusing different reflecting dishes to redirect the energy of theirrespective feeds. Alternatively, the orientation of the reflectingdishes can be configured such that the analog beams generate a clusterthat covers a contiguous geographical area on the Earth's surface. Insome implementations, the analog beams are generated such that theirfootprints overlap to some degree, e.g., either partially or completely,in the cluster. In such cases, digital beams are formed by combining theoverlapping analog beams in the cluster. In some implementations, theanalog beams are generated such that their footprints arenon-overlapping in the cluster. In such cases, digital beams are formedseparately from the analog beams in the cluster. The shape of thecluster can be varied by adjusting the relative positions of the analogbeams, as described in greater detail below. The satellite 105 then usesthe digital beamformers to generate digital beams within the coverageareas of the clusters.

In some implementations, the satellite 105 uses a set of steerableantennas, which are combined to generate digital beams. The antennas canbe steered using phase shifters, e.g., orientation of the antennas canbe changed by using different phase coefficients, or can be mechanicallysteered, e.g., using reflecting dishes, or mirror-based gimbals orbeam-director units. The antennas can also be steered using othermethods, e.g., by switching the antenna elements, or by using Risleyprisms, phased-array optics, or microelectromechanical systems (MEMS)using micro-mirrors.

The description in the following sections assume that some or all theanalog beams in a cluster overlap in full or in part. However, thetechniques described herein are also applicable in cases where some orall the analog beams in a cluster are non-overlapping.

In some implementations, the reflecting dishes in the satellite 105 aremounted on gimbals to enable the satellite to dynamically rotate thereflecting dishes to change the analog beam locations on the surface ofthe Earth after satellite deployment and during subsequent satelliteoperation. This ability to rotate the reflecting dishes enables thesatellite 105 to dynamically change its field of view during operationand, thereby, provides the satellite with much greater communicationsservices coverage flexibility than typical reflecting satellites in thatthe satellite 105 is able to place analog beams in a much greaterportion of the hemisphere of the Earth closest to the satellite byrotating the reflecting dishes as needed during satellite operation.Implementations using rotatable reflecting dishes are described ingreater detail in U.S. Pat. No. 9,083,426, titled “SatelliteBeamforming,” which is incorporated herein by reference in its entirety.

As noted previously, a subset of the feeds in the satellite 105 can beused for transmission in the forward direction from the satellite 105 tothe gateways 110 and 125, and the ground terminals 120 a-120 d. Thesefeeds are referred to as the forward link elements, transmit elements,or forward link feeds. Other feeds can be used for transmission in thereturn direction from the gateways 110, 125 and the ground terminals 120a-120 d to the satellite 105. These feeds are referred to as the returnlink elements, return link feeds, receive elements, or receiving feeds.

The gateways 110 and 125 are coupled to the network 135 through acommunications link 140. The network 135 can be a non-public datanetwork, a public data network or a combination of public and non-publicdata networks, e.g., the Internet. The communications link 140 can be ahigh-speed terrestrial connection, such as an optical connection withdata rates in the range of gigabits per second. Alternatively, thecommunications link 140 can be a satellite communications channelthrough a satellite that is different from the satellite 105. Thecommunications link 140 can be part of a closed network accessible onlyto components of the satellite communications system 100, or part of anopen network that connects the gateway 110 to the network 135.

The gateways 110 and 125 may include one or more modules that processsignals exchanged with the satellite elements for beamforming. In someimplementations, the gateways 110 and 125 may transmit signals to thesatellite 105 over the satellite return links for phase and/or gaincalibration for the return link and the forward link. This may be thecase, for example, when a GBBF system is employed. The signals used forphase and/or gain calibration may include unique code words thatidentify such signals as being configured for phase and/or gaincalibration. The satellite 105 may measure the phase and gain of thetransmitted calibration signals to enable calibration and/or pointingcorrection. The communications link 140 may be part of a closed networkaccessible only to components of the satellite communications system100, or may be part of an open network that connects the gateway 110 tothe network 135.

The ground terminals 120 a-120 d are computing devices or systems ableto communicate data to and from the satellite 105 over satellite links.In some implementations, one or more of the ground terminals 120 a-120 dare enterprise terminals. For example, a ground terminal can be asatellite dish that provides network connectivity to multiple devices ata location, such as an office building. In some implementations, one ormore of the ground terminals 120 a-120 d are individual user terminals.For example, a ground terminal can be a handheld mobile telephone or carphone, a laptop computer, desktop computer, or a phone booth. The groundterminals in separate coverage areas serviced by different clusters ofhybrid beams communicate with each other and with the gateways 110 and125 over the satellite 105 via the satellite links 145, 150 and 155.Each satellite link 145, 150 or 155 includes both an uplink to thesatellite 105 and a downlink from the satellite 105.

FIG. 2 illustrates an example of a configuration of feeds in aspacecraft 200 for hybrid beamforming. In some implementations, thespacecraft 200 is a satellite, for example, the satellite 105. As shown,the spacecraft 200 includes multiple antenna elements or feeds, such as202 a, 202 b, 202 c and 202 d. The feeds are divided into panels, suchas 204 a, 204 b, 204 c and 204 d.

Each feed, e.g., 202 a, 202 b, 202 c, or 202 d, uses a phase shifter toform an analog beam, in combination with one or more other feeds. A feedcan form one or more beams, by using a different phase shifter for eachbeam that it forms. The total number of feeds in the spacecraft 200 canrange from tens to hundreds and thousands. For example, Table I belowshows a configuration in which the spacecraft 200 has 8000 feeds.

The feeds are divided into panels, e.g., as 204 a, 204 b, 204 c and 204d, which is a subset of the feeds used for creating an analogbeamformer. The number of feeds can be different for different panels.For example, as shown, panel 204 a includes six feeds, panel 204 bincludes four feeds, while panel 204 d includes two feeds. However,panels 204 b and 204 c each has the same number of feeds, e.g., fourfeeds. The number of feeds shown in the various panels in FIG. 2 are forillustrative purposes only. In various implementations, the number offeeds in each panel can be different, and can range from a small number,as shown here, to hundreds or thousands.

Each panel forms a number of analog beams in the coverage area, withdifferent panels reusing the frequency spectrum for forming the analogbeams. Analog beams sharing the same frequency band overlap partially orfully, thereby forming a cluster, which is an area on the ground wheredigital beams are generated. Table I below shows an exemplaryconfiguration that is represented by panels per cluster*number ofclusters. For example, the first row shows four panels, each of whichforms analog beams for 16 clusters. In each of the 16 clusters, theanalog beams formed by a panel overlap with the analog beams formed byother panels. The 8000 feeds are divided amongst the four panels to formanalog beams. Each feed uses a subset of the 128,000 phase shifters thatare assigned to the feed to form analog beams in one or more clusters.

TABLE 1 Configuration (Panels Phase per cluster*Number Shifters FeedBeamformer of Clusters) (Thousands) Count Processor Clusters  4 × 16 1288000 64 Ports; 16 4 element Beamforming 4 × 8 64 8000 32 Ports; 8 4element Beamforming 8 × 4 32 8000 32 Ports; 4 8 element Beamforming

Each panel, e.g., each of 204 a, 204 b, 20 c and 204 d, is an analogbeamformer panel. Each analog beamformer forms analog beams by combiningthe phase, delay, or amplitude, or any combination of these parameters,of some or all the feeds included the panel. One or more of theseparameters are adjusted for each feed to combine into a single signal.Values of these parameter adjustments determine the location and theshape of the far-field coverage area on the Earth's surface, which isthe area to be covered by the satellite footprint.

One or more beamformer processors control some, or all, of the panels oranalog beamformers to adjust one or more of the phase, delay andamplitude parameters of the constituent feeds such that the analog beamsthat are formed by these feeds point to an overlapping far-fieldcoverage area on the Earth's surface. The overlapping coverage area isreferred to as a cluster. The analog beams in each cluster are fed toone or more digital beamformer processing logic, which form hybridbeams, e.g., digital beams that are generated by combining theamplitude, phase, or delay, or a suitable combination of theseparameters, of the analog beams. The hybrid beams have smaller coverageareas within the overlapping coverage area of the analog beams, e.g.,within the cluster.

In FIG. 2, a far field coverage area formed by analog beams generated byone or more panels of the spacecraft 200, e.g., panels 204 a, 204 b, 204c and 204 d, among others, is represented by 210. One or more analogbeams generated by the panels overlap in the far field coverage areawithin the region 212, which represents a cluster. One or more hybridbeams, e.g., 214 a, 214 b, 214 c and 214 d, are generated within thecluster region 212 by combining the overlapping analog beams to createdigital beams. As noted previously, each hybrid beam is a digital beamthat is generated by combining underlying analog beams.

As shown in FIG. 2, the hybrid beams can be of different shapes and/orsizes. For example, hybrid beams 214 a and 214 b are of the same sizeand shape. However, hybrid beam 214 c is of a different size and shapethan the beams 214 a and 214 b. Hybrid beam 214 d is also of a differentsize and shape than the hybrid beams 214 a, 214 b and 214 c.

As described in detail below, the number of hybrid beams that are formedin a cluster can vary from cluster to cluster. For example, someclusters may have a large number of hybrid beams. Some clusters may haveonly a single hybrid beam that is formed by combing all the analog beamscorresponding to the cluster.

FIG. 3 illustrates an example of a hybrid beamformer processingcircuitry 302 in a spacecraft for generating hybrid beams, e.g., 314 a,314 b, 314 c and 314 d, among others. The spacecraft hybrid beamformerprocessing circuitry 302 includes K analog beamformers (K is an integerand K>0), such as 304 a, 304 b, 304 c and 304 d. The spacecraft hybridbeamformer processing circuitry 302 also includes a digital beamformer306. In some implementations, the spacecraft is a satellite, e.g.,satellite 105, and the processing circuitry 302 is present in thesatellite 105. The spacecraft hybrid beamformer processing circuitry 302is also referred to as hybrid beamformer 302.

In some implementations, the spacecraft hybrid beamformer processingcircuitry 302 includes a combined onboard processor with logic forcontrolling the analog beamformers to form analog beams, and logic forthe digital beamformer 306 to form digital beams. In someimplementations, the spacecraft hybrid beamformer processing circuitry302 includes separate onboard processors for controlling the analogbeamformers that are different from the digital beamformer 306. Thefollowing description is applicable both implementations.

Each analog beamformer, e.g., 304 a, 304 b, 304 c and 304 d, is a panelthat includes one or more feeds, as described above. In someimplementations, there are four analog beamformers (K=4), as shown inFIG. 3. However, in other implementations, there are different numbersof analog beamformers on the spacecraft (e.g., K=2, 5, 8, 13, 16, 24,among other values). In some implementations, the analog beamformerscorrespond to direct radiating array (DRA) panels. Each DRA panelincludes one or more feeds. In some implementations, the analogbeamformers correspond to parabolic reflectors. In such cases, eachanalog beamformer is a parabolic reflector that includes one or morefeeds. Other configurations of the analog beamformers are also possible.

The spacecraft includes N×N feeds (N is an integer and N>0). In someimplementations, N is on the order of hundreds or thousands, e.g., asshown in Table I. In the processing circuitry 302, the N×N feeds aredivided evenly among the four analog beamformers 304 a, 304 b, 304 c and304 d, such that each analog beamformer includes N/2×N/2 feeds. However,in some implementations, the number of feeds included in an analogbeamformer can vary, e.g., as discussed above with respect to the panels204 a, 204 b, 204 c and 204 d.

As shown, in some implementations, each analog beamformer, e.g., 304 a,304 b, 304 c and 304 d, controls the constituent N/2×N/2 feeds togenerate Y analog beams (Y is an integer and Y>0). In someimplementations, an analog beamformer generates each analog beam bycombining each of the constituent feeds. This is the case, for example,when there are Y phase shifters per feed. In other implementations, ananalog beamformer generates each analog beam by combining a subset ofthe constituent feeds. In such cases, the number of phase shifters perfeed can be less than Y. Alternatively, each feed can have Y phaseshifters, but the analog beamformer does not use all the feeds for eachbeam. In some implementations, different analog beamformers can generatedifferent numbers of analog beams.

As shown, in some implementations, the K analog beamformers generate upto a total of K*Y analog beams. Analog beams from one or more analogbeamformers overlap with each another in a far field coverage area,forming a cluster. For example, analog beams 312 a, 312 b, 312 c and 312d, among others, overlap in part or in full to generate a cluster 314.In some implementations, one or more analog beams from each of the Kanalog beamformers overlap to form a cluster. In some implementations, asingle cluster is generated by combining one analog beam from eachanalog beamformer. In such cases, up to a total of Y clusters arepossible, since each analog beamformer can generate up to Y beams. Insome implementations, one or more analog beams from a subset of the Kanalog beamformers overlap to form a cluster. For example, in somecases, one analog beam per analog beamformer across half the analogbeamformers overlap in a cluster, thereby forming up to 2Y clusters.

In some implementations, the overall frequency spectrum available to thespacecraft is reused by each analog beamformer, which divides theavailable frequency spectrum between the analog beams that thebeamformer generates. Analog beams from different analog beamformersthat have the same frequency band overlap to form a cluster. In suchcases, the frequency band in each cluster is different from thefrequency band in adjacent clusters. However, frequency bands can bereused amongst non-adjacent clusters.

In some cases, the spacing between the panels or analog beamformers isconfigured to maximize the communications capacity of the spacecraft byallowing a tighter cluster of beams, while limiting digital side lobes.The digital side lobes are also referred to as grating lobes, which arecaused by the wide spacing between panel centers. The wider the spacing,the closer in are the digital side lobes or grating lobes to the mainbeam. In this context, maximizing the communications capacity refers toachieving a highest communications capacity of a communications linkcreated by the satellite that is achievable in view of the physicalconstraints of the satellite hardware, or the communications medium(e.g., air), or both. In some implementations, maximizing thecommunications capacity refers to achieving an upper limit data ratethat is configured by the satellite administrator.

A larger spacing between the panels results in clusters that are closertogether, allowing for a tighter cluster of beams, which therebyimproves communication capacity. The digital beam gains are also closerto beam center of the underlying analog beams, and the gain roll offbefore a beam can re-use the frequency band is reduced. The largerinter-panel spacing also reduces the digital beam size, while improvingthe maximum capacity. However, too much increase in spacing canadversely impact performance due to interference from digital sidelobes, which are described below.

As shown, in some implementations, the K analog beamformers feed the K*Yanalog beams to the digital beamformer 306 to generate hybrid beams. Foreach overlapping cluster of analog beams, the digital beamformer 306divides the corresponding frequency band into channels, and generates adigital beam for each channel by combining the analog beams in thecluster, as described previously. The digital beamformer 306 cangenerate potentially hundreds or thousands of digital beams covering thecluster area defined by the EOC of the analog beams in the cluster. Forexample, as shown in FIG. 3, the digital beamformer 306 generates hybridbeams, such as 314 a, 314 b, 314 c and 314 d, in the cluster 314, whereeach hybrid beam is assigned a frequency channel that is a part of theoverall frequency band covered by the analog beams in the cluster 314,such as analog beams 312 a, 312 b, 312 c and 312 d. Although only onedigital beamformer 306 is shown, in some implementations, the spacecrafthybrid beamformer processing circuitry 302 includes more than onedigital beamformer.

In the above manner, the spacecraft hybrid beamformer processingcircuitry 302 functions as a hybrid beamformer that creates hybrid beamsby generating digital beams using combinations of overlapping analogbeams. In doing so, the hybrid beamformer allows the analog beamformers,e.g., 304 a, 304 b, 304 c and 304 d, to support a large number of feedsand the digital beamformer e.g., 306, to create a large number of beamsfor providing coverage. The number of clusters that are formedcorrespond to the number of regions that have to be covered forcommunications coverage. As opposed to pure digital beamforming, wheredigital beams can be created in any region, in hybrid beamforming, thedigital beamformers in the spacecraft are constrained to create thehybrid beams, i.e., the digital beams, within the coverage areas of theunderlying analog beams. The analog beamformers combine the analog beamsto provide the contours of the coverage areas in which the digital beamsare generated.

As described above, with the same analog beamforming hardware to createK beams, the hybrid beamformer supports up to K times the bandwidth; Ktimes the coverage area; and higher EOC gain over most beams. Thespacecraft hybrid beamformer processing circuitry 302 thereby addressesthe hardware constraints of analog beamformers to support a large numberof beams (e.g., in the order of hundreds or thousands), since everyanalog beam requires one phase shifter per feed, and addresses theprocessing constraints of digital beamformers to process a large numberof feeds.

In general, in some implementations, for a spacecraft with N×N feeds andK panels/analog beamformers, the N×N feeds can be evenly divided amongthe K analog beamformers such that each analog beamformer getsN/√{square root over (K)}×N/√{square root over (K)} feeds. If eachanalog beamformer forms Y analog beams, then a total of K*Y analog beamsare generated by the processing circuitry on board the spacecraft. Insome implementations, K*Y analog beams are generated for transmittingdata, and another K*Y analog beams are generated in the receivedirection. For either direction, the K*Y analog beams are fed to digitalbeamformers. In some implementations, one or more onboard payloadprocessors include Y digital beamformers, e.g., one for each analog beamin a cluster. In some implementations, each digital beamformer includescircuitry for K×K beamforming, e.g., K inputs and K outputs. For eachcluster, the Y digital beamformers channelizes the available bandwidthinto Z channels (Z is an integer and Z>0), and generates Z digital beamswithin the cluster coverage area by combining the analog beams thatoverlap to form the cluster. Each digital beam is assigned one of the Zchannels. Accordingly, a total of K*Y*Z hybrid beams are formed.

As an example, in some cases, the processing circuitry in a satellite,e.g., satellite 105, includes 8 panels or analog beamformers, each with16×16 feeds. The 8 analog beamformers correspond to 8 parabolicreflectors, with the feeds for each analog beamformer coupled to aseparate parabolic reflector. Each analog beamformer forms 16 analogbeams. The analog beamformer circuitry in the satellite thereforegenerates 128 analog beams in the transmit direction, and 128 analogbeams in the receive direction. The transmit and receive analog beamsare fed to a digital beamformer, which includes two processors. Eachdigital beamformer processor, which is capable of 8×8 beamforming, has64 input ports and 64 output ports, with 2.5 GHz bandwidth per port.Each processor divides the available bandwidth in to 12.5 MHz channels.A total of up to 22,000 hybrid beams, e.g., digital beams formed bycombining the analog beams, can be generated with this configuration ofthe satellite processing circuitry for hybrid beamforming.

In some implementations, each hybrid beam covers analog beamwidthcorresponding to 3 decibels (3 dB). As described above, the availableanalog bandwidth in a cluster is divided into a large number of digitalbeams, e.g., the digital beams in each cluster can range from tens tohundreds or thousands. In some implementations, the number of digitalbeams generated in a cluster depends on a target degradation in signalpower from the beam peak, e.g., center, of a digital beam to the edge ofthe digital beam. For example, in some cases, the target degradation insignal power is 0.5 dB such that the digital edge of cell is near thebeam peak. In these cases, a sufficient number of digital beams aregenerated such that the digital edge of cell. less than 0.5 dB downcompared to the beam peak. In some implementations, the peak gain of adigital beam, e.g. the beam peak, is 10*log₁₀(K) dB higher than analogbeam, where K is the number of analog beamformers, as described above.

In the above manner, a spacecraft, e.g., a satellite, performs hybridbeamforming. To summarize, the satellite uses transmit and receiveantennas that utilize a hierarchical structure, in which multiple feedsare arranged in a panel, and multiple panels coordinate to form beams tocover a target area. Each panel uses analog amplitude (or gain), delayor phase adjustment, or any combination of these, to combine signals formultiple feeds in the panel, to create analog beams in clusters in thefar field covering regions of the target area. The values of theamplitude (or gain), delay or phase adjustments determine positions ofthe far-field coverage areas. Digital beamformer processors useamplitude (or gain), delay or phase adjustment, or any combination ofthese, to combine analog beam signals from one or more panels togenerate hybrid beams in each cluster. In this manner, the analogbeamformer panels and the digital beamformer processors form hybridbeams in a hierarchical structure. The analog and digital amplitude (orgain), delay or phase adjustments are configurable, and modification ofthese parameters allows the clusters of coverage areas in the far fieldto be moved.

In some implementations, the spacecraft, e.g., satellite 105, combineselectronically steerable antennas with digital beams for hybridbeamforming. In such cases, the electronically steerable antennas areused in place of feeds to delineate coverage areas in which clusters ofdigital beams are formed.

FIGS. 4A and 4B present comparative illustrations of coverage providedrespectively by analog and hybrid beams in a target area 400 on theEarth's surface. FIG. 4A shows analog beams, such as 402 a, 402 b and402 c, among others, covering regions in the target area 400, which iswithin the footprint 420 of a spacecraft, e.g., satellite 105. Theanalog beams are formed by analog beamformers described above. FIG. 4Bshows clusters of hybrid beams, such as 410 a, 410 b and 410 c, amongothers, providing coverage in similar regions in the target area 400. Asdescribed above, a hybrid analog/digital beamformer forms the hybridbeams in each cluster, e.g., 410 a, 410 b and 410 c, by combiningcol-located or overlapping analog beams in the corresponding cluster togenerate digital beams, each of which occupies a frequency channel inthe overall spectrum covered by the analog beams in the cluster.

As shown in FIG. 4B, each cluster, e.g., 410 a, 410 b and 410 c,includes many hybrid, i.e., digital beams. By forming analog beams ineach cluster using a subset of the total feeds in the spacecraft (e.g.,using one or more beams per analog beamformer), the coverage area ofeach cluster is larger, as shown, compared to the coverage area of ananalog beam that is formed using all the feeds in the spacecraft. FIG. 5presents a comparative illustration of examples of coverage areas 502and 504 respectively provided by a pure analog beam and overlappinganalog beams formed using a hybrid beamformer. Considering aconfiguration for a spacecraft with N×N feeds, the coverage area 502represents an area covered by an analog beam formed using all N×N feeds,e.g., when analog-only beamforming is used. If the spacecraft includes Kpanels or analog beamformers, in which the N feeds are evenly dividedamong the K analog beamformers such that each analog beamformer getsN/√{square root over (K)}×N/√{square root over (K)} feeds, then coveragearea 504 represents an area covered by overlapping analog beams in acluster that includes one analog beam from each analog beamformer, e.g.,when hybrid beamforming is used. Each analog beam in the coverage area504 is formed by 1/K feeds if all the feeds in a panel are used to formthe analog beam.

The beamwidth from the peak to the EOC in both coverage areas 502 and504 is the same (e.g., 3 dB beamwidth EOC). Given the larger coveragearea in hybrid beamforming, the peak gain of the overlapping analogbeams in the cluster is lower than the peak gain of analog-onlybeamforming. For example, the peak gain of the analog beams in thecoverage area 504 is 10 log₁₀(K) dB lower compared to that of the analogbeam in the coverage area 502. As a numerical example, in someimplementations, the peak gain of the analog beams in the coverage area504 is 6 dB less than the peak gain of the analog beam in the coveragearea 502.

The loss in peak gain for the analog beams in hybrid beamforming can berecovered by the hybrid beams. For example, in the configurationdescribed above in which K analog beams overlap in a cluster (e.g., oneanalog beam from each of K clusters) and are combined to form hybridbeams, then the peak gain of each hybrid beam is 10 log₁₀(K) dB higherthan the underlying analog beams in the cluster.

Although FIGS. 4A and 4B show approximately circular coverage areas, insome implementations, the coverage areas can be arbitrarily shaped toeffectively cover users. FIG. 6 illustrates an example of hybridbeamforming to fully cover a non-circular shaped region 600. Aspacecraft, e.g., satellite 105, provides coverage to the region 600. Insome implementations, the region 600 is part of a larger target area,e.g., the target area 400. A hybrid beamformer on board the spacecraftcreates multiple analog beams, such as 602 a, 602 b and 602 c, amongothers, that are spread out to fully cover the region 600. As shown, allthe analog beams are not co-located. For example, analog beams 602 a and602 c partially overlap with one another, and analog beams 602 b and 602c partially overlap with one another, but analog beams 602 a and 602 bdo not overlap. By spreading the analog beams in this manner, the hybridbeamformer can cover an arbitrarily shaped target area.

The hybrid beamformer combines the analog beams, e.g., 602 a, 602 b and602 c, among others, to create many (e.g. hundreds or thousands) ofunique hybrid (e.g., digital) beams, such as 604 a, 604 b and 604 c. Thehybrid beamformer generates a sufficient number of hybrid beams so thatthe edge of cell of the digital beams is near the beam peak (e.g., lessthan 0.5 dB down from the beam peak to edge of cell), as describedpreviously. However, since the analog beams are spread out, the peakgain of a hybrid beam is lower, compared to the case where all theanalog beams are co-located (e.g., in a circular coverage area).

FIGS. 7A and 7B illustrate examples of different cluster shapes that canbe formed using hybrid beamforming. As described previously, a clusteris an area on the ground that can support hybrid beams. A cluster isformed by overlapping, partly or fully, analog beams formed by analogbeamformers, e.g., 304 a, 304 b, 304 c and 304 d shown previously. FIG.7A shows that a cluster 702 can be approximately circular, e.g., whenall the analog beams overlap with one another. A cluster can also bearbitrarily shaped, e.g., cluster 704. This is the case, for example,when the analog beams are spread out to cover the target area, such asdescribed with respect to the region 600. In some implementations,clusters of different shapes, such as clusters 702 and 704, are formedto cover different regions of the target area, with these clusterscoexisting. In some implementations, the shapes of the clusters aredetermined to meet specified performance requirements at EOC.

A number of hybrid beams, which are digital beams formed by combiningthe analog beams in a cluster, are generated for each cluster. Forexample, cluster 702 includes hybrid beams 702 a, 702 b and 702 c, amongothers, while cluster 704 includes hybrid beams 704 a, 704 b and 704 c,among others. The number of hybrid beams can range from tens to hundredsor thousands. In some implementations, the hybrid beams are tightlypacked together to provide continuous coverage in the regioncorresponding to the cluster, e.g., the hybrid beams 604 a, 604 b and604 c, among others, in the region 600. In some implementations, thehybrid beams are less densely packed to cover only areas where users arepresent. For example, the hybrid beams 702 a, 702 b and 702 c, amongothers, in the cluster 702 are less tightly packed than the hybrid beams604 a, 604 b and 604 c. In some cases, the hybrid beams are spread outeven further to cover selected portions in a cluster. For example, thereare wide gaps between the hybrid beams 704 a, 704 b and 704 c, amongothers, in the cluster 704, indicating areas where no beam coverageexists. This can be the case when coverage is provided in less populatedareas. In some implementations, clusters with different densities ofhybrid beams coexist to cover different regions in a target area, wherethe different regions have different coverage requirements. For example,clusters 702 and 704 can coexist with the respective configurations ofhybrid beams as shown.

As noted previously, hybrid beamforming clusters can be K times largerin area than for similar analog beams in analog-only beamforming (whereK is the number of analog beamformers). The full frequency spectrum(uplink and downlink) can be re-used multiple times, and up to K timesin some cases. The hybrid beams match the yield of the underlying analogbeams with same or higher gain. In some implementations, wider bandwidthusage by the hybrid beams provides higher capacity because lowermodulation codes are much more power efficient compared to highermodulation codes.

FIG. 7B shows some examples of varying cluster shapes that can beachieved using hybrid beamforming. A hybrid beamformer, e.g., thespacecraft hybrid beamformer processing circuitry 302, can form clustersshaped as in clusters 710 a and 710 f, square clusters such as 710 b,parallelogram shaped clusters such as 710 c and 710 d, orsemi-cylindrical shaped clusters such as 710 e, among other clustershapes. Each of the clusters 710 a, 710 b, 710 c, 710 d, 710 e and 710 fcluster shapes can fully re-use the frequency spectrum available forhybrid beamforming. The entire spectrum can be assigned to any part of acluster. Combinations of these shapes overlapped in a single cluster canbe created by segmenting the frequency band, and assigning each bandsegment to a different cluster shape. Size of any dimension of a clustercan also be adjusted. For example, in some implementations, up to +/−10%of the optimal shape of a cluster can be adjusted with sacrificing 0.5dB in gain, but without any change in the carrier to interference (C/I)ratio.

FIG. 8 illustrates an example of a process 800 for forming hybrid beams.In some implementations, the process 800 is performed by hybridbeamformer processing circuitry in a spacecraft, e.g., by the spacecrafthybrid beamformer processing circuitry 302, which includes one or moreanalog beamformer processors 304 a, 304 b, 304 c and 304 d, and one ormore digital beamformer processors such as 306. As described previously,in some implementations, the spacecraft is an orbiting satellite, suchas the satellite 105. Accordingly, the following section describes theprocess 800 with respect to the spacecraft hybrid beamformer processingcircuitry 302. However, the process 800 also can be performed by otherprocessing circuitry configurations, and/or by other types ofspacecraft.

In some implementations, the hybrid beamformer processing circuitry,referred to henceforth interchangeably either as hybrid beamformer orprocessing circuitry, executes one or more instructions to perform theprocess 800. These instructions are stored in memory, e.g., flashmemory, hard disk or some other suitable memory, which is coupled to thehybrid beamformer on board the spacecraft. Alternatively, in someimplementations, the instructions are sent to the hybrid beamformer onboard the spacecraft from the ground, e.g., through satellite gateway110 or 125.

The process 800 starts at 802, in which a target area for communicationscoverage is determined. For example, the hybrid beamformer processingcircuitry 302 determines an area on the Earth's surface forcommunications coverage, such as target area 400. In someimplementations, information about the target area, e.g., coordinates ofthe area, are sent to the hybrid beamformer on board the spacecraft,e.g., as part of telecommunications commands from ground stations viathe satellite gateways 110 or 125.

At 804, the hybrid beamformer divides the target area into a pluralityof regions. For example, the hybrid beamformer processing circuitry 302divides the target area 400 into a plurality of regions. In someimplementations, the plurality of regions includes the region 600. Insome implementations, the plurality of regions is determined based onthe presence of user population in the target area, or thecommunications requirement in various regions, or both. For example,only regions in the target area where users are present are selected insome cases, while uninhabited areas are avoided. Additionally oralternatively, in some cases, areas where communications equipment arepresent, such as data gathering apparatus, or areas where users arepredicted to be present within a known time period, such as a shippingchannel in an ocean, are selected in some cases.

At 806, the hybrid beamformer controls a subset of panels of feeds onthe spacecraft to generate analog beams for each region, thereby forminga cluster, with each panel generating one or more analog beams of thecluster. For example, the hybrid beamformer processing circuitry 302controls the analog beamformers 304 a, 304 b, 304 c and 304 d togenerate analog beams for each identified region of the target areawhere communications coverage is to be provided. An analog beamformergenerates an analog beam by combining the phase, delay, gain, or anycombination of these, of the feeds in the corresponding panel of theanalog beamformer.

As described previously, in some implementations, one or more analogbeams formed by each analog beamformer are provided to each region. Insome cases, each region is provided one analog beam from each analogbeamformer. If an analog beamformer can form Y analog beams (e.g., thereare Y phase shifters per feed in the panel), then up to Y clusters canbe generated, thereby covering up to Y regions. With K panels present onthe spacecraft, a total of up to K*Y analog beams can be generated, asdescribed earlier.

In some implementations, one or more analog beams formed by a subset ofanalog beamformers are provided to each region. For example, analogbeams formed by half the analog beamformers, such as 304 a and 304 b,cover a first group of regions, while analog beams formed by the otherhalf the analog beamformers, such as 304 c and 304 d, cover a secondgroup of regions, which are different from the first group of regions.As described previously, in such cases, up to 2*Y clusters can beformed, using the example configuration above. Other configurations arealso possible, as described further below. For example, all the analogbeams from all the panels can be formed to overlap with each other insome cases, thereby covering a single region.

In some cases, all the analog beams in a cluster can overlap, e.g., asshown with respect to analog beams 312 a, 312 b, 312 c and 312 d. Insome cases, the analog beams in a cluster can be spread out, e.g., asshown with respect to analog beams 602 a, 602 b and 602 c. The shape ofa cluster is determined by the number of analog beams present in thecluster, and the way the analog beams overlap. For example, if all theanalog beams overlap to the greatest extent, such as analog beams 312 a,312 b, 312 c and 312 d, then a circular shaped cluster is generated,such as cluster 702. However, if the analog beams are spread out, thenclusters of arbitrary shapes can be formed, such as clusters 704, 710 a,710 b, 710 c, 710 d, 710 e and 710 f. In some implementations, thenumber of analog beams in a region, and the relative positions of theanalog beams in the region, are determined to maximize the coverage gainover the region.

At 808, the hybrid beamformer generates, in each cluster, one or morehybrid beams from the analog beams in the cluster, with each hybrid beamcorresponding to a digital beam formed by combining one or more analogbeams in the cluster. For example, the hybrid beamformer processingcircuitry 302 controls the digital beamformer 306 to generate, for eachregion, digital beams by combining the analog beams in the clustercorresponding to the region. The digital beamformer combines themagnitude, delay, or phase, or any combination of these parameters, ofthe analog beams in the region to form the digital beams for the region.

As described previously, each cluster of hybrid beams provides coverageover a wider area compared to analog beams formed using analog-onlybeamforming, e.g., as shown by clusters 410 a, 410 b and 410 c incomparison to analog beams 402 a, 402 b and 402 c. Depending on thecoverage requirement, the relative positions of hybrid beams in acluster can be different from that of other clusters. The coveragerequirement depends, on the gain roll off from the peak to the EOC ofthe hybrid beams, or the locations of users, among other factors, asdescribed previously. For example, the hybrid beams can be tightlypacked in a cluster, e.g., as shown with respect to hybrid beams 604 a,604 b and 604 c. In some implementations, the hybrid beams are tightlypacked so that edge of digital beam roll off is negligible (e.g. lessthan 0.5 dB). Alternatively, the hybrid beams can be more looselypacked, e.g., as shown with respect to hybrid beams 702 a, 702 b and 702c, or the hybrid beams can be spread out such that some hybrid beams aredistant from other hybrid beams in a cluster, e.g., as shown withrespect to hybrid beams 704 a, 704 b and 704 c.

In some implementations, additional bandwidth is put into hybrid beamsthat require higher capacity. The available frequency spectrum within aregion can be completely re-used up to K times (when there are K analogbeamformers), depending on the relative distribution of the hybrid beamswithin the region. In some implementations, the frequency spectrum isreused a lower number of times than K, depending on the target C/I andthe relative distribution of the hybrid beams within the region.

At 810, the hybrid beamformer checks whether every region in the targetarea is covered. For example, after generating hybrid beams for aselected region in the target area 400, the hybrid beamformer processingcircuitry checks whether hybrid beams for other identified regions inthe target area are yet to be generated. If every region is not covered,e.g., one or more regions are remaining for which hybrid beams are yetto be generated, then the hybrid beamformer repeats the process at 806and 808 until all the identified regions are covered. When hybrid beamshave been generated for all the identified regions, then the hybridbeamforming generation process 800 ends.

In some implementations, one or more clusters of hybrid beams coexist toprovide simultaneous coverage to multiple regions, as describedpreviously. However, in some cases, the number of regions to be coveredcan be more than the number of clusters that can be simultaneouslysupported by the analog beamformers in the spacecraft, e.g., thesatellite 105, or regions may be far apart such that all the regions arenot simultaneously within the footprint of the spacecraft at a time. Insuch cases, the hybrid beamformer circuitry on board the spacecraftcovers all the regions by forming clusters of hybrid beams in thedifferent regions in successive intervals of time, with a subset of theregions being covered at a time interval. The spacecraft “hops” from onelocation to another location through a sequence of locations in the farfield coverage area. In some implementations, air interfaces orcommunications protocols, such as DVBS2X, can synchronize transmissionswith satellite hopping to provide a service to both hopped clusterlocations.

The spacecraft, e.g., the satellite 105, can hop from one location toanother using one of several different hopping patterns, which include:(i) analog only hopping; (ii) analog/digital hopping; and (iii) digitalonly hopping. In analog only hopping, the spacecraft systematicallychanges the analog coefficients for the feeds in each panel to result inthe cluster of hybrid beams hopping from one location to another. Thishas the effect of a cluster hopping from one location to another due tochange in the coverage area of the overlapping analog beams. Therelative positions and shapes of the hybrid beams within a clusterremain unchanged. In some implementations, analog only hopping isachieved by the analog beamformers making a single delay or gainadjustment to coefficients of the analog beams before the analog beamsare fed to the digital beamformer processor. In some implementations,delay and gain adjustments on each analog signal ensures that therelative positions and performance of the digital beams are unchanged.

As an example of analog only hopping, in some cases, the cluster 410 a(or the cluster 410 b, 410 c, 702 or 704, among others) hops from afirst location in a first time interval to a second location in the nexttime interval. The analog beamformer processors, e.g., 304 a, 304 b, 304c and/or 304 d, adjust the coefficients of the analog beams in thecluster 410 such that the terrestrial region covered by these beamschanges. However, the coefficients of the digital beams formed by thedigital beamformer using these analog beams remain unchanged, andtherefore the relative positions and shapes of the hybrid beams withinthe cluster 410 a remain unchanged.

In some implementations, analog only hopping occurs in a scheduledrepeating loop. For example, a cluster of digital beams will providecoverage to a first location for a first period of time; and thenre-orient the corresponding analog beams to provide coverage to a secondlocation for a second period of time, and so on, before returning to thefirst location to again provide coverage for the first period of time.In some implementations, the first period and second period arepreselected. In some implementations, the first period and second periodcan be dynamically determined, depending on the coverage requirements.In some implementations, one or more periods are the same. In otherimplementations, every period is different.

In analog/digital hopping, the hybrid beamformer processing circuitry onboard the spacecraft changes both analog and digital coefficients toresult in a cluster of hybrid beams hopping from one location toanother. The relative positions and shapes of the digital beams within acluster change, along with change in the location (and, in someimplementations, shape) of the analog coverage area. In someimplementations, the analog coefficients are adjusted on a scheduledrepeating basis. The digital beam coefficients are also adjusted on ascheduled repeating basis, with adjustments to the digital beamcoefficients synchronized with adjustments to the analog coefficients.In some implementations, analog/digital hopping results in changes tobeam-to-beam routing as well as channel bandwidths.

As an example of analog/digital hopping, in some cases, the cluster 702hops from a first location in a first time interval to a second locationin the next time interval. The analog beamformer processors, e.g., 304a, 304 b, 304 c and/or 304 d, adjust the coefficients of the analogbeams in the cluster 410 such that the terrestrial region covered bythese beams changes, and the shape of the cluster also changes to thatof cluster 704. The digital beamformer processor 306 also adjusts thecoefficients of the digital beams that are formed, and therefore therelative positions and/or shapes of the hybrid beams within the cluster702 change, for example from the relative orientations of hybrid beams702 a, 702 b and 702 c to the relative orientations of hybrid beams 704a, 704 b and 704 c.

FIGS. 8A and 8B illustrate examples of analog only hopping 820 andanalog/digital hopping 830. As shown in FIG. 8A, in analog only hopping,a cluster 822 hops from a first location represented by 822 a to asecond location represented by 822 b, and then to a third locationrepresented by 822 c, by changing the orientations of the analog beams.However, there is no change in the relative positions and shapes of thehybrid beams within the cluster, such that the overall shape of thecluster 822 remains unchanged. The example in FIG. 8A further shows thatthe cluster 822 performs analog only hopping in a scheduled repeatingloop, revisiting locations it had covered in previous time intervals.For example, after covering locations 822 b and 822 c, the cluster 822returns to provide coverage to location 822 a in a new time period.

FIG. 8B shows that in analog/digital hopping, a cluster 832 hops from afirst location represented by 832 a to a second location represented by832 b, and then to a third location represented by 832 c, by changingthe orientations of the analog beams. At the same time, the relativepositions and shapes of the hybrid beams within the cluster change, suchthat the overall shape of the cluster 832 in each location is different.For example, the shape of the cluster 832 in location 832 a is differentfrom the shape of the cluster 832 in location 832 b, which is differentfrom the shape of the cluster 832 in location 832 c.

In digital only hopping, the hybrid beamformer processing circuitry onboard the spacecraft changes the digital coefficients to result indigital coverage areas hopping within the analog coverage area. In suchcases, the relative positions and shapes of the hybrid beams within acluster change, but the analog coverage area does not change. Forexample, in some implementations, the digital beamformer 306 changes thedigital coefficients for the cluster 702, such that the relativepositions of the hybrid beams 702 a, 702 b and 702 c within the cluster702 changes from one time interval to another. However, the terrestrialregion covered by the underlying analog beams in the cluster 702 doesnot change.

In some implementations, the hopping patterns described above areenabled for any uplink or any downlink communications channel. In suchcases, a router in the processor on board the spacecraft facilitates aconnection between a downlink and an uplink. In some implementations,the duration of each hop is configurable, e.g., by an operator of thespacecraft, such as a satellite network administrator. In such cases,the time interval of coverage provided by the spacecraft in some regionscan be different than the coverage time interval provided in some otherregions. In some implementations, the analog coefficients, or digitalcoefficients, or both, are configurable for each hop. In such cases, theshape and size of a cluster can vary from one hop to another. Further,the relative positions and sizes of the digital beams in a particularcluster can also vary from one hop to another.

In some implementations, the hybrid beams formed by a hybrid beamformercan of four beam types. A first hybrid beam type is full cluster beams,also referred to as “type 1” beams, which are clusters of digital beamsthat move over the coverage area and that are created using all thepanels. In type 1 beams, a cluster includes one analog beam per panelfor all the panels in the spacecraft, and digital beams are generatedwithin the footprint of overlapping analog beams in the cluster.

When type 1 beams are used, a cluster can be resized and/or reshaped asrequired. Type 1 beams support reuse of the frequency bands up to Ktimes, where K is the total number of panels or analog beamformers, witheach contributing an analog beam to a cluster. For type 1 beams, up to Pfull cluster beams can be supported due to frequency reuse, whereP=K*number of frequencies. Type 1 beams are used to provide coverage forhigh capacity areas that are bandwidth limited locally and power limitedglobally.

Type 1 beams can be used to provide coverage with either a uniformlaydown of beams, or a non-uniform laydown of beams. In uniform laydownof type 1 beams, the beam pattern is repeated across all digital beamsin each cluster. A uniform or ordered pattern is used within a cluster,e.g., as shown with respect to hybrid beams 314 a, 314 b, 314 c and 314d, but the pattern can vary from one cluster to another cluster. Thehybrid or digital beams are distributed across the cluster using afrequency reuse plan. Uniform laydowns can support frequency re-use ofthe spectrum K times, where K is the number of panels or analogbeamformers. Ground terminals can access the spacecraft, e.g., satellite105, from any location within the cluster.

In non-uniform laydown of type 1 beams, hybrid beams within a clustercan have different arbitrary patterns. In some implementations,non-uniform laydown is used when the exact locations of ground terminalsare known. The beam patterns within a cluster are optimized with respectto the demand profile and the geographic distribution of terminals. Thefrequency reuse depends on the distribution of ground terminals in acluster.

FIG. 9 shows an example use case where type 1 beams are used in clusters910, 920 and 930 in a non-uniform laydown. The clusters 910, 920 and 930covers users in close proximity within each cluster, as shown. Thehybrid beams in each cluster are formed to cover user populations in anon-uniform laydown. The clusters 910, 920 and 930 reuse the respectiveavailable frequency spectrum 2.1 times. For example, in cluster 910,hybrid beams 912 a, 912 b and 912 c reuse the same frequency channelthree times; hybrid beams 914 a, 914 b and 914 c reuse another frequencychannel three times; and hybrid beam 916 uses its own frequency channel.In cluster 920, hybrid beams 922 a and 922 b reuse the same frequencychannel twice; hybrid beams 924 a and 924 b reuse another frequencychannel twice; and hybrid beam 926 a and 926 b reuse a third frequencychannel twice. In cluster 930, hybrid beams 932 a, 932 b and 932 c reusethe same frequency channel three times; hybrid beams 934 a and 934 breuse another frequency channel two times; and hybrid beam 936 uses athird frequency channel.

A second hybrid beam type is partial cluster beams, also referred to as“type 2” beams, which are clusters of beams that move over the coveragearea and that are created out of a subset of panels. In type 2 beams, acluster includes analog beams generated by some of the panels in thespacecraft, and digital beams are generated within the footprint ofoverlapping analog beams in the cluster. A cluster with type 2 beams canbe resized and/or reshaped as needed. Type 2 beams can be used in highcapacity areas that are bandwidth limited locally and when only a subsetof panels are available for use. This can be the case, for example, whena spacecraft, e.g., satellite 105, is configured to cover a large numberof locations using a limited number of beams, such as when the satellite105 is a Low Earth Orbit (LEO) satellite that is moving in its orbit.

A third hybrid beam type is simple beams, also referred to as “type 3”beams, which are similar to beams formed in an analog direct radiatingarray that uses the same number of total feeds. However, the type 3beams can be narrow band. All the panels are used to create one analogbeam, and a single digital beam is generated from the analog beam.

A simple beam can be formed into any shape. During a pass over a targetregion, a simple beam can be reshaped to maintain a constant coveragearea and Power Flux Density (PFD) levels. A single satellite spacecraftcan support up to K simple beams, where K is the number of panels in thesatellite. Each simple beam can completely reuse the frequency spectrumavailable to the spacecraft. In some cases, simple beams are used inpower limited areas that have plenty of frequency spectrum.

A fourth hybrid beam type is split beams, also referred to as “type 4”beams, which are beams with double the beam width of a simple beam. Fortype 4 beams, the total number of panels is split into groups, and eachgroup of panels is used to create a different beam in a manner similarto that of simple beams. For example, in some implementations, two type4 beams are created—one from half of the panels, and the second from theother half of the panels. A split beam can be formed into any shape.Similar to the simple beams, split beams can be narrow band beams. Asplit beam has twice the minimum area of simple beam, but 3 dB lessmaximum gain than a simple beam. In some cases, split beams are used forspectrum limited satellite views where users are spread out over a widearea. Split beams are also useful for users near nadir of a coverageregion where PFD requirements are lower.

Type 3 or simple beams, and type 4 or split beams, are single hybridbeams and not clusters of hybrid beams. Therefore, within the regioncovered by type 3 beams or type 4 beams, the available frequency is onlyused once. Accordingly, type 3 or type 4 beams are useful when userlocations are packed so close that frequency reuse cannot be supported.However, hardware resources (e.g. panels) that are used for type 3 ortype 4 beams can be moved and shared as required as the gain andcoverage requirements vary due to movement of the spacecraft over thetarget regions. In some implementations, any or all of type 1, type 2,type 3 and type 4 beams are used to cover a target area, depending ontraffic and coverage requirements.

In some implementations, as the spacecraft, e.g., satellite 105, fliesover a target area, hardware resources, e.g., panels of feeds, aretransferred among different types of beams and clusters. For example, atone position of the satellite along its orbit, the hybrid beamformercircuitry on board the satellite uses more panels for a first cluster tocover a first region, and a lesser number of panels for a second clusterto cover a second region that is within the footprint of the satellite.As the satellite moves, at a different position of the satellite alongits orbit, the on board hybrid beamformer circuitry dynamicallyreconfigures the assignment of panels and increases the panels for thesecond cluster, while decreasing the number of panels for the firstcluster. In some implementations, the hybrid beamformer achieves thereconfiguration by reassigning some of the panels from generating analogbeams for the first cluster to generating analog beams for the secondcluster. The dynamic reconfiguration is performed to allow the capacityin each cluster to be continuously maximized.

As a spacecraft, e.g., the satellite 105, moves along its trajectory andthereby across a coverage area on the ground, beam requirements to coverusers in the coverage area can change. For example, at one point in thetrajectory, users in a particular coverage region can be far away. Asthe satellite moves closer to the coverage region due to its movementalong its orbit, the users in the coverage region gradually becomecloser to the satellite. When the satellite is directly overhead(referred to as “nadir”), the distance from the satellite to the usersin the coverage region is the shortest of all positions along thesatellite's orbit (here, positions refer to positions of the satellitealong its orbit from where there is line of sight to the coverage regionsuch that the satellite can provide communications coverage).Accordingly, at the nadir, the amount of power and/or antenna gainrequired by the satellite to close the communications link is the leastcompared to other positions of the satellite along the orbit. However,the angular area required to cover the users is larger compared to atother positions of the satellite along its orbit. In view of this, whenthe satellite is at the nadir of a coverage region, the satellite canprovide coverage to the region using a lower number of panels, comparedto other positions of the satellite along the orbit. By using a lowernumber of panels, a lower gain but a wider angular area are achieved.

When the satellite is near the horizon relative to the coverage region(e.g., EOC), the distance from the satellite to the users in thecoverage region is the longest compared to at other positions of thesatellite along its orbit. In this situation, the amount of power and/orantenna gain required to close the communications link is the greatest,compared to at other positions of the satellite along its orbit. At thesame time, the angular area required to cover the users in the region issmaller compared to at other positions of the satellite along its orbit.In view of this, when the satellite is at the EOC of a coverage region,the satellite can provide coverage using more panels, compared to otherpositions of the satellite along the orbit. This results in a highergain and a narrower angular area.

Since, in some implementations, the satellite provides coverage tomultiple regions, as one coverage region moves closer to nadir andanother coverage region moves closer to the horizon due to movement ofthe satellite along its orbit, the hybrid beamformer processingcircuitry on board the satellite transfers panels from providingcoverage to one area to providing coverage to another area. The transferof panels is done dynamically and seamlessly so that there is minimalimpact to the communications performance experienced by the user on theground, and such that the underlying air interface (e.g., thecommunication protocol used to communicate between the satellite and aground terminal) suffers minimal negative effects.

FIGS. 10A and 10B illustrate examples of dynamic resource transfer inhybrid beamforming to provide communications coverage in multipleregions. FIG. 10A illustrates an example of resource transfer from type4 beams to type 3 beams in clusters 1012 and 1014, as a satellite, e.g.,satellite 105, moves along its orbit such that the satellite footprintchanges from footprint 1010 to footprint 1020 and then to footprint1030.

The footprints 1010, 1020 and 1030 indicate areas on the ground overwhich the satellite provides coverage, depending on the satellite'sposition along its orbit. The hybrid beamformer on board the satellitegenerates hybrid beams to provide communications coverage to two regions1012 and 1014 within the target area. As shown, in a first time period,when the satellite footprint is 1010, the region 1012 is near the EOC ofthe footprint, while the region 1014 is near the nadir, e.g., close tobeing directly under the satellite's orbital position. In this context,a coverage region is at the nadir of the spacecraft when the spacecraftis directly overhead the coverage region. In contrast, a coverage regionis at the EOC of the spacecraft when the spacecraft is positioned suchthat the coverage region is at the boundary of an area covered by thespacecraft's communications footprint in its present position. Moreresources, e.g., panels, are generally needed closer to EOC to providecoverage with acceptable gain, compared to when the satellite isdirectly overhead. Accordingly, the hybrid beamformer assigns fourpanels to cover the region 1012 that is near the EOC, but assigns onepanel to cover the region 1014 near the nadir. The hybrid beamformerforms type 4 or split hybrid beams using the four panels in the clusterfor region 1012, and forms a type 3 or simple hybrid beam using the onepanel in the cluster for region 1014.

Due to movement of the satellite, in a second time period, the footprintof the satellite changes to 1020, as a result of which the nadir movesaway from the region 1014, while moving closer to the region 1012. Inthis position, the satellite can cover region 1012 with a lesser numberof panels than when at footprint 1010, but needs more panels toeffectively cover region 1014. Accordingly, the hybrid beamformerdynamically reassigns one panel from covering the region 1012 tocovering the region 1014. Therefore, in footprint 1020, the hybridbeamformer forms type 4 or split beams using the three panels in region1012, and also forms type 4 or split beams using the two panels inregion 1014.

Due to further movement of the satellite, in a third time period, thefootprint of the satellite changes from 1020 to 1030, as a result ofwhich the region 1014 is near the EOC of the satellite footprint, whilethe region 1012 is close to the nadir. In this position, the satellitecan cover region 1012 with the least number of panels than at any otherposition, since the satellite is almost directly overhead the region1012. However, the satellite needs the most number of panels toeffectively cover region 1014, since the region 1014 is near the EOC.Accordingly, the hybrid beamformer further dynamically reassigns twopanels from covering the region 1012 to covering the region 1014,thereby having only one panel for region 1012, but four panels forregion 1014. Therefore, in footprint 1020, the hybrid beamformer forms atype 3 or simple beam using the remaining panel in region 1012, butforms type 4 or split beams using the four panels in region 1014.

In the above manner, as the position of a first region changes from EOCto nadir (e.g., region 1012) and the position of a second region changesfrom nadir to EOC (e.g., region 1014) due to satellite movement, panelsare dynamically transferred from the first region to the second regionto maximize performance and capacity. This effectively reduces the gainin the first region and expands its coverage to match PFD requirements.At the same time the gain in the second region is improved and thecoverage area is narrowed.

FIG. 10B illustrates an example of resource transfer from type 4 beamsto type 2 beams in clusters 1022 and 1024, as a satellite, e.g.,satellite 105, moves along its orbit such that the satellite footprintchanges from footprint 1040 to footprint 1050.

The footprints 1040 and 1050 indicate areas on the ground over which thesatellite provides coverage, depending on the satellite's position alongits orbit. The hybrid beamformer on board the satellite generates hybridbeams to provide communications coverage to two regions 1022 and 1024within the target area. As shown, in a first time period, when thesatellite footprint is 1040, the region 1022 is at the EOC of thefootprint 1040. Since more resources, e.g., panels, are needed closer toEOC to provide coverage with acceptable gain, the hybrid beamformerassigns four panels to the region 1022, and forms type 4 or split beamsusing the four panels in region 1022.

Due to movement of the satellite, in a second time period, the footprintof the satellite changes to 1050, as a result of which the nadir iscloser to the region 1022, while a new region 1024 comes within thesatellite footprint at the EOC. In this position, the satellite cancover region 1022 with the least number of panels than at any otherposition, since the satellite is almost directly overhead the region1022. However, the satellite needs the most number of panels toeffectively cover region 1024 near the EOC. Accordingly, the hybridbeamformer dynamically reassigns three panels from covering the region1022 to covering the region 1024, thereby having only one panel forregion 1022, but three panels for region 1024. In footprint 1050, thehybrid beamformer forms a type 3 or simple beam using the remainingpanel in region 1022, but forms type 2 or partial cluster beams usingthe three panels in region 1024. This effectively reduces the gain inregion 1022, but expands its coverage to match PFD requirements, whilehardware resources are made available so that the region 1024 can beeffectively covered.

FIG. 11 illustrates an example of a process 1100 for resource transferin hybrid beamforming. In some implementations, the process 1100 isperformed by hybrid beamformer processing circuitry in a spacecraft,e.g., by hybrid beamformer processing circuitry 302, which includes oneor more analog beamformer processors 304 a, 304 b, 304 c and 304 d, andone or more digital beamformer processors such as 306. As describedpreviously, in some implementations, the spacecraft is an orbitingsatellite, such as the satellite 105. Accordingly, the following sectiondescribes the process 1100 with respect to the hybrid beamformerprocessing circuitry 302. However, the process 1100 also can beperformed by other processing circuitry configurations, and/or by othertypes of spacecraft.

In some implementations, the hybrid beamformer processing circuitryexecutes one or more instructions to perform the process 1100. Theseinstructions are stored in memory, e.g., flash memory, hard disk or someother suitable memory, which is coupled to the hybrid beamformer onboard the spacecraft. Alternatively, in some implementations, theinstructions are sent to the hybrid beamformer on board the spacecraftfrom the ground, e.g., through satellite gateway 110 or 125.

In the following sections, the process 1100 is described with respect totwo positions of the spacecraft—the nadir and the edge of coverage(EOC). These two positions are mentioned for ease of explanation only.The process 1100 is also applicable to other positions of thespacecraft, e.g., halfway between nadir and EOC, or any location betweenthe nadir and the EOC.

The process 1100 starts at 1102, in which a target area forcommunications coverage is determined. For example, the hybridbeamformer processing circuitry 302 determines an area on the Earth'ssurface for communications coverage, such as target area 400. In someimplementations, information about the target area, e.g., coordinates ofthe area, are sent to the hybrid beamformer on board the spacecraft,e.g., as part of telecommunications commands from ground stations to thesatellite 105 via the satellite gateways 110 or 125.

At 1104, the hybrid beamformer divides the target area into a pluralityof regions, including a first region and a second region. For example,the hybrid beamformer processing circuitry 302 divides the target areainto a plurality of regions. In some implementations, the plurality ofregions includes the regions 1012 and 1014, or the regions 1022 and1024. In some implementations, the plurality of regions is determinedbased on the presence of user population in the target area, or thecommunications requirement in various regions, or both. For example,only regions in the target area where users are present are selected insome cases, while uninhabited areas are avoided. Additionally oralternatively, in some cases, areas where communications equipment arepresent, such as data gathering apparatus, or areas where users arepredicted to be present within a known time period, such as a shippingchannel in an ocean, are selected in some cases.

At 1106, the hybrid beamformer determines, at a first time, that thefirst region corresponds to the edge of coverage (EOC) and the secondregion corresponds to the nadir of the spacecraft. For example, in afirst time interval, the satellite 105 is at an orbital position thatcorresponds to the footprint 1010. In this position of the satellite105, the hybrid beamformer processing circuitry 302 on board thesatellite determines that the region 1012 is near the EOC of thesatellite footprint, while the region 1014 is near the nadir of thesatellite footprint, i.e., almost directly under the satellite'sposition.

At 1108, at the first time, the hybrid beamformer controls (i) a firstsubset of feed panels on the spacecraft to generate a first group ofanalog beams for the first region in a first cluster and (ii) a secondsubset of feed panels on the spacecraft to generate a second group ofanalog beams for the second region in a second cluster. For example, inthe first time interval, when the satellite 105 is in the orbitalposition corresponding to footprint 1010, the hybrid beamformerprocessing circuitry 302 assigns four panels to cover the region 1012and one panel to cover the region 1014. The hybrid beamformer 302 usesthe four panels or analog beamformers to generate analog beams in afirst cluster for the region 1012, and uses the one panel or analogbeamformer to generate analog beams in a second cluster for the region1014.

At 1110, the hybrid beamformer generates (i) one or more digital beamsin the first cluster from the analog beams in the first cluster, and(ii) one or more digital beams in the second cluster from the analogbeams in the second cluster. For example, in the first time interval,after generating the analog beam in the first cluster for the region1012, the hybrid beamformer processing circuitry 302 combines the analogbeams in the first cluster to generate one or more digital beams tocover the region 1012. Similarly, after generating the analog beamcorresponding to second cluster for the region 1014, the hybridbeamformer processing circuitry 302 combines the analog beams in thesecond cluster to generate one or more digital beams to cover the region1014. In this manner, the hybrid beamformer forms hybrid beams in thefirst and second clusters for the regions 1012 and 1014 respectively. Asdescribed previously, in some implementations, the hybrid beamformerforms split beams in the region 1012, and a simple beam in the region1014.

At 1112, at a second time following the first time, the hybridbeamformer determines, that the first region corresponds to the nadirand the second region corresponds to the EOC of the spacecraft. Forexample, in a second time interval, the satellite 105 is at an orbitalposition that corresponds to the footprint 1030 (having moved throughthe footprint 1020 position in an intermediate time interval). In thisposition of the satellite 105, the hybrid beamformer processingcircuitry 302 on board the satellite determines that the region 1012 isnear the nadir of the satellite footprint 1030, while the region 1014 isnear the EOC of the satellite footprint 1030.

At 1114, at the second time, the hybrid beamformer controls (i) a thirdsubset of feed panels on the spacecraft to generate a third group ofanalog beams for the first region in a third cluster and (ii) a fourthsubset of feed panels on the spacecraft to generate a fourth group ofanalog beams for the second region in a fourth cluster. For example, inthe second time interval, when the satellite 105 is in the orbitalposition corresponding to footprint 1030, the hybrid beamformerprocessing circuitry 302 dynamically reassigns panels from covering theregion 1012 to cover the region 1014, since the former region requiresless panels for coverage near the nadir but the latter region requiresmore panels for coverage near the EOC, as described previously. In someimplementations, the hybrid beamformer 302 assigns one panel to coverthe region 1012, but assigns four panels to cover the region 1014, wheresome of these four panels were used to provide coverage in the region1012 earlier in the first time interval. The hybrid beamformer 302 usesthe one panel or analog beamformer to generate analog beams in a thirdcluster for the region 1012, and uses the four panels or analogbeamformers to generate analog beams in a fourth cluster for the region1014. In some implementations, the number of analog beams in the thirdcluster is different from the number of analog beams in the firstcluster to cover the same region 1012, and the number of analog beams inthe fourth cluster is different from the number of analog beams in thesecond cluster to cover the same region 1014. However, in otherimplementations, the number of analog beams in the third cluster is samefrom the number of analog beams in the first cluster, and the number ofanalog beams in the fourth cluster is same as the number of analog beamsin the second cluster.

At 1116, the hybrid beamformer generates (i) one or more digital beamsin the third cluster from the analog beams in the third cluster, and(ii) one or more digital beams in the fourth cluster from the analogbeams in the fourth cluster. For example, in the second time interval,after generating the analog beam in the third cluster for the region1012, the hybrid beamformer processing circuitry 302 combines the analogbeams in the third cluster to generate one or more digital beams tocover the region 1012. Similarly, after generating the analog beamcorresponding to fourth cluster for the region 1014, the hybridbeamformer processing circuitry 302 combines the analog beams in thefourth cluster to generate one or more digital beams to cover the region1014. In this manner, the hybrid beamformer forms hybrid beams in thethird and fourth clusters for the regions 1012 and 1014 respectively. Asdescribed previously, in some implementations, the hybrid beamformerforms a simple beam in the region 1012, and split beams in the region1014. Accordingly, the number of hybrid beams in the third cluster isdifferent from the number of hybrid beams in the first cluster to coverthe same region 1012, and the number of hybrid beams in the fourthcluster is different from the number of hybrid beams in the secondcluster to cover the same region 1014. In the above manner, the hybridbeamformer processing circuitry 302 on board the satellite 105 transfershardware resources, e.g., panels from covering one region to covering adifferent region as the relative positions of these regions with respectto the satellite changes due to the satellite's movement.

As mentioned previously, the process 1100 is described above withrespect to two positions of the spacecraft—the nadir and the edge ofcoverage (EOC), which two positions are mentioned for ease ofexplanation only. The process 1100 is also applicable to other positionsof the spacecraft, e.g., halfway between nadir and EOC, or any locationbetween the nadir and the EOC. The number of panels that are transferredfrom covering a region that moves closer to the spacecraft (i.e.,towards the nadir) to covering a region that moves farther away from thespacecraft (i.e., towards the EOC) due to the motion of the spacecraft,varies depending on the position of the spacecraft along its trajectory.Certain locations require different power and footprints than otherlocations. As the spacecraft moves from the proximity of a first of suchlocations to a second of such locations, resource transfer, i.e.,transfer of one or more panels, are triggered to best address the newand different power and footprint needs of the two locations. Changingfrom one relative location having a first set of communicationcharacteristics or attributes for servicing that area to anotherlocation having a second set of communication characteristics orattributes for servicing that area triggers the spacecraft to performresource transfer such that a different number of panels would beadvantageous to properly service the locations as their locations changerelative to the satellite.

As described in the above sections, a spacecraft, e.g., satellite 105,can dynamically provide coverage flexibility while in orbit. FIGS.12A-12D illustrate examples of coverage flexibility provided by aspacecraft, e.g., satellite 105, using hybrid beamforming. In somecases, a cluster is resized—either increased in size or decreased insize. Additionally or alternatively, a cluster can be reshaped. FIG. 12Ashows an example of a cluster 1200 that is resized and/or reshaped atdifferent time intervals of coverage. The cluster is reshaped from afirst square shape 1202 to a second circular shape 1204. The cluster isresized in the circular shape among sizes 1204, 1206 and 1208 at varioustime intervals. The cluster is further reshaped from a circular shape1208 to an arbitrary shape 1210 at another time interval. In someimplementations, when a cluster is resized or reshaped, there is achange in the bandwidth capacity of the cluster. For example, when acluster is decreased in size, the bandwidth capacity can be reduced.Alternatively, when a cluster is increased in size, the bandwidthcapacity can be increased.

In some implementations, the hybrid beamformer moves clusters in orbitto any location across the Earth's surface. FIG. 12B shows an example ofa group of clusters moved from a first configuration 1220 to a secondconfiguration 1222. In some implementations, each cluster in theconfiguration 1220 or 1222 includes a large number (e.g., hundreds) ofhybrid beams. In some implementations, the frequency band is reused manytimes in each cluster. In some implementations, each cluster includes asingle polarization.

In some implementations, the hybrid beamformer increases the number ofclusters dynamically. FIG. 12C shows an example of increasing a numberof clusters between groups 1232, 1234 and 1236. At a first timeinterval, the hybrid beamformer 312 generates a first number ofclusters, including clusters 1232 a, 1232 b and 1232 c, in group 1232.In some implementations, the clusters 1232 a, 1232 b and 1232 c havedual polarization and double the capacity of clusters in the othergroups 1234 and 1236.

At a second time interval, in group 1234, the hybrid beamformer 312generates a second number of clusters, including clusters 1234 a, 1234 band 1234 c. Subsequently, at a third time interval, in group 1234, thehybrid beamformer 312 splits some of the clusters from group 1232 togenerates a third group of clusters, such as clusters 1236 a and 1236 b.In some implementations, a cluster from the second group is split toform a number of clusters in the third group. The number can be two orfour, among others. In some implementations, the clusters 1236 a and1236 b in the third group have less gain and less frequency reusedcompared to the clusters, e.g., 1234 a, 1234 b and 1234 c, in the secondgroup. In some implementations, the clusters in the first, second andthird groups can be generated by time hopping across the Earth's surfaceduring different time intervals, as the satellite 105 moves in itsorbit.

In some implementations, the hybrid beamformer reconfigures a singlecluster as multiple clusters to create clusters by splitting. Forexample, in some cases, the hybrid beamformer forms two clusters byusing a subset of the analog beamformer panels for each cluster, asdescribed previously. For a P×Q array of beamformer panels (P×Q areintegers>0), the hybrid beamformer generates one cluster using P/2×Qpanels and the second cluster using the other P/2×Q panels. In a similarmanner, the hybrid beamformer can use other subsets of panels to createmultiple sets of clusters out of hardware resources that were designedfor a single high gain cluster.

In some implementations, the hybrid beamformer can change theorientations of the analog beamformers, relative to the Earth's surface.In such cases, arbitrarily steerable clusters can be formed. FIG. 12Dshows an example of steerable clusters, e.g., 1252 a, 1252 b, 1252 c,1254 a, 1254 b, 1254 c and 1256, formed using hybrid beamforming. Asshown, the clusters can be circular in shape, e.g., clusters 1252 a,1252 b and 1252 c. Additionally or alternatively, the clusters can besquare in shape, e.g., clusters 1254 a, 1254 b and 1254 c. Additionallyor alternatively, the clusters can be any arbitrary shape, e.g., cluster1256, where a cluster is shaped to match the region to be covered. Theclusters 1252 a, 1252 b, 1252 c, 1254 a, 1254 b, 1254 c and 1256 can besteered to any location on the Earth's surface.

The hybrid beamformer can form a larger number of clusters atreduced/lower gain. Additionally or alternatively, the hybrid beamformercan cover larger areas, or shaped areas, at reduced gain. The hybridbeamformer also can form smaller clusters.

As described previously, a target area can be divided into regions andeach region can be covered by a cluster of hybrid beams. In someimplementations, the clusters of hybrid beams covering regions in atarget area are arranged in rows and columns to provide contiguouscoverage in the target area. In some implementations, rows of clustersare shifted horizontally, or columns of clusters are shifted vertically,or both, to effectively cover a target area, e.g., a target area that isof arbitrary shape.

FIG. 13 illustrates an example of a group of clusters 1300 shiftedhorizontally, or vertically, or both, to cover a target area. A hybridbeamformer, e.g., the hybrid beamformer processing circuitry 302, cancover a target area by forming a group of clusters of hybrid beams, suchas the group of clusters 1300. Individual clusters in the group arearranged in rows and columns, e.g., rows 1320 a, 1320 b and 1320 c, andcolumns 1330 a, 1330 b and 1330 c. In some implementations, the rows andcolumns are arranged in a square configuration, e.g., configuration1310, to cover the target area.

In some implementations, one or more rows of clusters are shiftedhorizontally to cover the target area. For example, in configuration1320, rows 1320 a, 1320 b and 1320 c, among others, are shiftedhorizontally. The vertical arrangement of clusters, while adjusted bythe row shifting, remains a vertical arrangement. Accordingly, thearrangement of the clusters in one or more columns are maintained, butthe heights of the columns can be different.

In some implementations, one or more columns of clusters are shiftedvertically to cover the target area. For example, in configuration 1330,and columns 1330 a, 1330 b and 1330 c, among others, are shiftedvertically. The horizontal arrangement of clusters, while adjusted bythe column shifting, remains a horizontal arrangement. Accordingly, thearrangement of the clusters in one or more rows are maintained, but thewidths of the rows can be different.

In some implementations, both rows and columns are shifted, respectivelyhorizontally and vertically. There can be slight differences inperformance depending on horizontal or vertical shift. For example, thegain can change by a small degree. Generally, the performance remainsnearly the same as in the case of no horizontal or vertical shift.Frequency reuse is the same and does not change due to horizontal orvertical shift.

In some implementations, hybrid beams in a cluster that formed using oneanalog beam from each analog beamformer panel have the maximum gain.However, in some implementations, the hybrid beams in a cluster are notformed using analog beams from all panels on the array.

If the analog beamformer panels are arranged in a P×Q array, then themaximum frequency reuse of a cluster is P times Q (P columns by M rowsof analog beamforming panels). In some implementations, to generatehybrid beams within a cluster at a single frequency, hybrid beams withina predetermined range of a line parallel to the rows in the cluster arelimited to a length within a preselected R degrees, and hybrid beamswithin a predetermined range of a line parallel to the panel columns arelimited to a length within a preselected S degrees (where R and S arenatural numbers). R is the distance between side lobes that appear inthe horizontal direction, while S is the distance between side lobesthat appear in the vertical direction. In some implementations, sidelobes that are difficult to suppress appear along the vertical axis.Accordingly, the range limit S degrees is selected to avoid co-channelbeam interference with the side lobes in the vertical direction.

FIG. 13A illustrates a graphical example of signal spread of co-channelhybrid beams, e.g., hybrid beams 1342 and 1344, and corresponding sidelobes, e.g., side lobes 1346 a and 1346 b. Hybrid beam 1342 is a desiredhybrid beam in a cluster, while co-channel hybrid beams, e.g., hybridbeams that share the same frequency channel as hybrid beam 1342, arecollectively indicated as 1344. Side lobes 1346 a and 1346 b are formedby the co-channel beams. As shown, the desired beam 1342 is R degreesremoved from the side lobe 1346 b in the horizontal direction, and Sdegrees removed from the side lobe 1346 a in the vertical direction.

As shown in FIG. 13A, in some implementations, up to P co-channel hybridbeams are distributed along a horizontal line parallel to the clusterrows over a length no more than R degrees and nominally to aroundR*P/(P+1) degrees. In some implementations, up to Q co-channel hybridbeams are distributed along a vertical line parallel to the clustercolumns over a length no more than S degrees and nominally to aroundS*Q/(S+1) degrees. In the example shown in FIG. 13A, P=Q=4.

Horizontal lines of hybrid beams can be shifted with respect to eachother as long as the hybrid beams do not violate the line segment lengthrules. Similarly, vertical lines of hybrid beams can be shifted withrespect to each other as long as the hybrid beams do not violate theline segment length rules. In some implementations, beam distributionsare not uniformly distributed in a row or in a column.

Multiple frequencies are configured in a manner similar to the above.Once the hybrid beams are generated, the rows and columns can be shiftedto fill in gaps, if any, between the hybrid beams. FIG. 13 showsexamples of hybrid beams formed with the above principles. In someimplementations, clusters of hybrid beams have gaps between the hybridbeams, or a non-uniform arrangement of beams, or both.

FIGS. 14A-14E illustrate an example of covering regions in a target areaby hybrid beamforming using groups of clusters. As shown in FIG. 14A, ata first time, a hybrid beamformer, e.g., the hybrid beamformer 302 onboard a spacecraft, such as satellite 105, forms a plurality of analogbeams from the analog beamformer panels in the spacecraft. For example,the hybrid beamformer 302 forms analog beams 1410 a, 1410 b and 1410 c,among others, to cover a region in the target area. The analog beams areformed using some or all of the analog beamformers 304 a, 304 b, 304 cand 304 d. In some implementations, one beam from each analog beamformeris positioned and shaped over a desired coverage region in the targetarea. In other implementations, different numbers of beams fromdifferent analog beamformers are positioned and shaped over the desiredcoverage region.

The hybrid beamformer 302 feeds the analog beams to one or more digitalbeamformer processors, e.g., digital beamformer 306, which generatesdigital beams by combining the analog beams, as described previously.FIG. 14B shows a cluster 1420 of digital beams that is generated fromthe analog beams 1410 a, 1410 b and 1410 c to cover a desired region inthe target area. The digital beams in the cluster 1420 are arranged inrows, e.g., 1420 a, 1420 b and 1420 c, among others, and columns, e.g.,1430 a, 1430 b and 1430 c, among others.

In some implementations, the width of any row in a cluster is less thana preselected row width (e.g., R degrees), and the height of any columnis less than a preselected column height (e.g., S degrees). As notedpreviously, in some implementations, the column height is determinedbased on a distance between side lobes that appear in the horizontaldirection. The column height is selected to minimize the interferencefrom the side lobes. For example, as shown in FIG. 13A, if the verticaldistance between side lobes is within S degrees, then in someimplementations, up to Q co-channel hybrid beams are distributed along avertical column over a height no more than S degrees and nominally toaround S*Q/(S+1) degrees. Similarly, in some implementations, the rowwidth is determined based on a distance between side lobes that appearin the horizontal direction. The row width is selected to minimize theinterference from the side lobes. For example, as shown in FIG. 13A, ifthe horizontal distance between side lobes is within R degrees, then insome implementations, up to P co-channel hybrid beams are distributed ina row over a width no more than R degrees and nominally to aroundR*P/(P+1) degrees.

One or more of the rows are shifted horizontally, as shown in FIG. 14B,to conform to boundaries of the coverage region. Similarly, one or morecolumns can be shifted vertically to conform to the coverage boundaries.

After generating the cluster 1420 of hybrid beams to cover one desiredregion in the target area, the hybrid beamformer 302 generates hybridbeams to cover the next desired region in the target area. For example,as shown in FIG. 14C, the hybrid beamformer 302 generates analog beams1440 a, 1440 b and 1440 c, among others, which are steered or orientedto cover a second region in the target area that is adjacent to theregion covered by the cluster 1420. In some implementations, the analogbeams 1440 a, 1440 b and 1440 c correspond to second beams generated byeach analog beamformer panel. In some implementations, the analog beams1440 a, 1440 b and 1440 c are time hopped versions of analog beams inanother cluster, e.g., analog beams 1410 a, 1410 b and 1410 c. In someimplementations, the analog beams, e.g., 1440 a, 1440 b and 1440 c, inthe next region operate at a different hop time, polarization, orfrequency, or any suitable combination of these parameters, compared tothe analog beams in the next region, e.g., 1410 a, 1410 b and 1410 c, toavoid interference from side lobes from the cluster 1420.

The hybrid beamformer 302 subsequently generates digital beams bycombining the analog beams 1440 a, 1440 b and 1440 c, among others, asdescribed previously. FIG. 14D shows a cluster 1440 of digital beamsthat is generated from the analog beams 1440 a, 1440 b and 1440 c, amongothers to cover the desired region adjacent to the region covered by thecluster 1420. The digital beams in the cluster 1440 are also arranged inrows and columns, with the rows and columns in the cluster 1440 shiftedto fit with the rows and columns in the cluster 1420. In someimplementations, rows and columns are shifted such that co-channelhybrid beams (e.g., hybrid beams using the same frequency channel) areadjacent. In some implementations, neighboring clusters use differenttime hops, polarizations and/or time slots to avoid interference fromside lobes generated by adjacent clusters.

As shown in FIG. 14D, in some cases, the next boundary (e.g. coastline)of the target area is reached when forming a cluster, e.g., cluster1440. In such situations, in some implementations, the hybrid beamformer302 stretches of squashes hybrid beams across all the clusters whilemeeting row height and/or column height constraints described withrespect to FIG. 14B. For example, FIG. 14D shows that the hybrid beamsin clusters 1420 and 1440 stretched and squashed to reach the oppositecoastlines. The hybrid beamformer 302 can also eliminate some hybridbeams within one or more clusters to fully cover the target area.

Alternatively, in some implementations, the hybrid beamformer 302overlaps adjacent clusters without squashing either cluster. Asindicated above, hybrid beams in two adjacent clusters do not interferewith each other due to differences in one or more of frequency, timeslot or polarization. Further, overlapping clusters preserve fullcapacity of each cluster. Although FIG. 14D shows that the clusters arestretched/squashed, or overlapped, in the horizontal direction, asimilar technique can also be applied in the vertical direction.

The hybrid beamformer 302 repeats the process of forming clusters ofdigital beams until all desired regions within the target area arecovered. For example, as shown in FIG. 14E, after forming clusters 1420and 1440, the hybrid beamformer covers a third desired region with acluster 1450, as described with respect to FIGS. 14A-14D.

As noted above, in some implementations, neighboring clusters operateusing different frequency spectra, time slots, or polarization, or asuitable combination of these parameters, to avoid unwanted interferencefrom side lobes that are generated in the adjacent clusters. However, insome implementations, neighboring clusters share the same frequencyspectrum to suppress interference from side lobes. FIGS. 15A-15Cillustrate an example of sharing frequency spectrum between adjacentclusters in hybrid beamforming. Each of FIGS. 15A, 15B and 15B presentsa graph showing pattern cuts of a number of co-channel beams in a firstcluster that is indicated by 1502. In the example shown, the number ofco-channel beams is four. In each graph, the X-axis represents theangular cut (in degrees) of a satellite (e.g., satellite 105) beampattern on the Earth's surface due to orientation of the satellite withrespect to the Earth; and the Y-axis represents beam directivity in dB(decibels). In some implementations, the Y-axis represents gain in dBi(decibels relative to isotropic). FIG. 15A shows analog beams created ineach of two clusters 1502 and 1504 at different frequencies that areassigned to each cluster.

FIG. 15B shows hybrid beams that are created for cluster 1502 byapplying digital beamforming coefficients to analog beams generated forcluster 1502 by analog beamformers. In the example shown, the analogbeams for cluster 1502 are generated from 16 analog beamformer panels,and the hybrid beams are formed from all the analog beams in cluster1502. The formation of hybrid digital beams for cluster 1502 createsside lobes, e.g., side lobes 1510 a, 1510 b, 1510 c and 1510 d, inneighboring cluster 1502. In this context, the side lobes are digitalgrating lobes formed in a cluster, e.g., cluster 1502, that interferewith the hybrid beams in a neighboring cluster, e.g., cluster 1504.

As mentioned previously, to avoid interference from side lobes, in someimplementations, clusters 1502 and 1504 use different frequency spectra.However, in some implementations, the effect of side lobes is mitigatedby reusing frequencies across neighboring clusters. This is achieved byforming the digital beams for a first cluster using analog beams thatare assigned to the first cluster and also analog beams that areassigned to neighboring clusters of the first cluster.

FIG. 15C shows hybrid beams that are formed for cluster 1502 by applyingdigital beamforming coefficients for cluster 1502 to the analog beamsgenerated for both clusters 1502 and 1504. In the example shown, eachanalog beamformer panel is used twice—once to generate an analog beamfor cluster 1502 and then again to generate an analog beam for cluster1504. Hybrid beamforming for cluster 1502 is achieved with twice thenumber of analog beams as compared to the case shown in FIG. 15B, usingfrequencies that are shared between clusters 1502 and 1504. In a similarmanner, hybrid beamforming for cluster 1504 is achieved by combining theanalog beams for both clusters 1502 and 1504, using frequencies that areshared between clusters 1502 and 1504.

The side lobes formed for in cluster 1502 destructively interfere inphase with the side lobes formed in cluster 1504 due to use of the samefrequency bands in the two neighboring clusters. This results, for eachcluster, in lower gain of the side lobes, which is within an acceptablethreshold for interference in each cluster. For example, as shown inFIG. 15C, side lobes 1520 a, 1520 b, 1520 c and 1520 d are formed incluster 1502 when the hybrid beams are generated by combing the analogbeams for clusters 1502 and 1504 using the frequencies shared betweenthe two clusters. The directivity or gain of the side lobes 1520 a, 1520b, 1520 c and 1520 d are significantly less than the directivity or gainof the side lobes 1510 a, 1510 b, 1510 c and 1510 d. Accordingly, theinterference caused by the side lobes 1520 a, 1520 b, 1520 c and 1520 din cluster 1504 is less compared to the interference caused by the sidelobes 1510 a, 1510 b, 1510 c and 1510 d. In some implementations, theinterference from side lobes 1520 a, 1520 b, 1520 c and 1520 d is belowan interference threshold for cluster 1504, and therefore the adverseeffects of the side lobes 1520 a, 1520 b, 1520 c and 1520 d are withinacceptable levels.

FIGS. 16A-16C provide comparative examples of communications coverageusing different cluster frequencies and shared cluster frequencies. FIG.16A shows a target area 1600 in which desired regions are covered bygroups of analog beams forming clusters, such as clusters 1602 a, 1602b, 1602 c, 1602 d and 1602 e; 1604 a, 1604 b, 1604 c and 1604 d; 1606 a,1606 b and 1606 c; and 1608 a, 1608 b and 1608 c. Each square in FIG.16A represents a cluster, with different shadings indicating one or moreof different frequencies, polarizations or time hops used in theclusters. Clusters of similar shading therefore use the same frequency,polarization and time hop.

The circle 1610 represents the contour of the main lobe of the analogbeams for the center cluster 1602 e. Within each cluster area are hybridbeams, e.g., digital beams formed by combing the analog beams in thecluster, that fully fill the cluster area. As described previously, oneor more hybrid beams within each cluster can have different frequencychannels that are sub-bands of the combined frequency spectrum of theanalog beams forming the cluster. Additionally, one or more hybrid beamswithin each cluster can have the same frequency channel that is asub-band of the combined frequency spectrum of the analog beams formingthe cluster. In some implementations, the hybrid beams in a clusterreuse the frequency spectrum available to the cluster.

As shown in FIG. 16A, in some implementations, communications coverageis provided by adjacent clusters that use one or more of differentfrequencies, polarizations or time hops to minimize interference in theneighboring clusters. For example, clusters 1606 a, 1602 c, 1604 b and1608 b are adjacent clusters. Each of these clusters uses one or more ofa different frequency, polarization or time hop than the adjacentclusters. Similarly, clusters 1604 b and 1602 d are adjacent clustersand therefore each of them uses one or more of a different frequency,polarization or time hop than the other cluster.

Non-adjacent clusters, however, can use the same frequency, polarizationand time hop since they do not interfere with one another. For example,as shown, clusters 1602 c and 1602 d are non-adjacent clusters, whileclusters 1602 c and 1604 b, and 1604 b and 1602 d, are pairs of adjacentclusters. Therefore, 1602 c and 1602 d share the same frequency,polarization and time hop. However, cluster 1604 b has one or more offrequency, polarization or time hop different from clusters 1602 c and1602 d.

The approach of providing coverage shown in FIG. 16A—adjacent clustershaving one or more of frequency, polarization or time hop different,while non-adjacent clusters can share the same frequency, polarizationor time hop—is used when beamforming with just the analog beamsassociated with each cluster, e.g., analog beams centered over thecluster area. This is the case, for example, when analog beam 1610 isused for hybrid beamforming in cluster 1602 e, but not used for hybridbeamforming in other clusters.

The overlapping main lobes of different neighboring clusters use one ormore of different frequencies, polarizations or time hops to avoidinterference. However, clusters that are outside the main lobe of thecenter cluster can reuse the same frequency as the main lobe of thecenter cluster. Interference is controlled by adjusting the side lobesof the analog beams using complex coefficients (e.g. a phase oramplitude taper).

As an illustrative example, FIG. 16B shows a schematic diagram of analogbeam lobes 1622 a, 1624 a and 1626 a in neighboring clusters 1622, 1624and 1626, respectively. Cluster 1622 is a center cluster of digitalbeams, and beam lobe 1622 a is the main analog beam lobe of the centercluster 1622. Cluster 1624 is adjacent to the center cluster 1622. Lobe1624 a, which is the main analog beam lobe in the cluster 1624, uses oneor more of a different frequency, polarization or time hop than the mainbeam lobe 1622 a in the neighboring cluster to avoid interference.Cluster 1626 neighbors cluster 1624, but is non-adjacent with the centercluster 1622. Analog beamforming used to reduce side lobes and allow forsharing of parameters with center cluster. Accordingly, lobe 1626 a,which is the main analog beam lobe in the cluster 1626, can sharefrequency spectrum, time hops and polarization with the beam lobe 1622 ain the center cluster 1622.

In some implementations, communications coverage is provided by clustersin which a plurality of adjacent clusters use the same frequency,polarization and time hop. For example, FIG. 16C shows a target area1630 in which clusters corresponding to the coverage regions, e.g.,clusters 1630 a, 1630 b, 1630 c, 1630 d, 1630 e, 1630 f, 1630 g, 1630 h,1630 i, 1630 j, 1630 k, 16301 and 1630 m, among others, share thefrequency, polarization and time hop. In some implementations, theclusters corresponding to all the coverage regions in the target area1630 use the frequency, polarization and time hop. In someimplementations, a subset of the clusters corresponding to all thecoverage regions in the target area 1630 use the frequency, polarizationand time hop.

In the target area 1630, a cluster that shares the same frequency,polarization and time hop with neighboring clusters generates hybridbeams using analog beams corresponding to the cluster itself, and alsousing analog beams of one or more neighboring cluster(s). For example,as shown, cluster 1630 c shares the same frequency, polarization andtime hop with clusters 1630 b and 1630 d. Cluster 1630 c forms digitalbeams by combining analog beams corresponding to cluster 1630 c, andincluding analog beams corresponding to one or more of clusters 1630 band 1630 d. This is similar to the hybrid beam forming described withrespect to clusters 1502 and 1504. The interference of distant clustersis controlled by adjusting the side lobes of the analog beams usingcomplex coefficients.

Within each cluster area digital beams fully fill the area. The digitalbeams within each cluster can have different frequency channels thatreuse the frequency spectrum of the underlying analog beams, e.g.,frequency spectrum shared by analog beams of the same cluster andneighboring cluster(s).

The approach of providing communications coverage using adjacentclusters sharing frequency, polarization and time hop, as described withrespect to FIG. 16C, enables reuse of a greater frequency spectrum,e.g., combination of the frequency spectra of analog beams assigned toneighboring clusters, compared to providing communications coverageusing adjacent clusters with different frequencies, polarizations ortime hops, as described with respect to FIGS. 16A and 16B. However, theformer option—shared frequencies between adjacent clusters—require moredigital processing, since the hybrid beamformer processing circuitry hasto process more analog beams to generate each digital beam.

FIG. 17 illustrates an example of a process 1700 for providingcommunications coverage to a plurality of regions a target area usinghybrid beamforming. In some implementations, the process 1700 isperformed by hybrid beamformer processing circuitry in a spacecraft,e.g., by hybrid beamformer processing circuitry 302, which includes oneor more analog beamformer processors 304 a, 304 b, 304 c and 304 d, andone or more digital beamformer processors such as 306. As describedpreviously, in some implementations, the spacecraft is an orbitingsatellite, such as the satellite 105. Accordingly, the following sectiondescribes the process 1700 with respect to the hybrid beamformerprocessing circuitry 302. However, the process 1700 also can beperformed by other processing circuitry configurations, and/or by othertypes of spacecraft.

In some implementations, the hybrid beamformer processing circuitry 302executes one or more instructions to perform the process 1700. Theseinstructions are stored in memory, e.g., flash memory, hard disk or someother suitable memory, which is coupled to the hybrid beamformer onboard the spacecraft. Alternatively, in some implementations, theinstructions are sent to the hybrid beamformer on board the spacecraftfrom ground stations, e.g., through satellite gateway 110 or 125.

The process 1700 starts at 1702, in which a target area forcommunications coverage is determined. For example, the hybridbeamformer processing circuitry 302 determines an area on the Earth'ssurface for communications coverage, such as a target area shown withrespect to FIGS. 14A-14E. In some implementations, information about thetarget area, e.g., coordinates of the area, are sent to the hybridbeamformer on board the spacecraft, e.g., as part of telecommunicationscommands from ground stations to the satellite 105 via the satellitegateways 110 or 125.

At 1704, the hybrid beamformer divides the target area into a pluralityof regions. For example, the hybrid beamformer processing circuitry 302divides the target area into a plurality of regions. In someimplementations, the plurality of regions includes regions correspondingto the clusters 1420 and 1440.

At 1706, the hybrid beamformer selects a first region of the pluralityof regions. For example, the hybrid beamformer 302 selects the regionshown in FIG. 14A.

At 1708, the hybrid beamformer controls panels of feeds on thespacecraft to generate analog beams in a first cluster for the firstregion, each panel generating one or more analog beams in the firstcluster. For example, the hybrid beamformer 302 controls the analogbeamformers 304 a, 304 b, 304 c and 340 d to generate a plurality ofanalog beams for the selected region, such as analog beams 1410 a, 1410b and 1410 c, among others, thereby forming a cluster 1420.

In some implementations, the hybrid beamformer 302 generates one or moreanalog beams from each analog beamformer 304 a, 304 b, 304 c and 340 d.In other implementations, the hybrid beamformer 302 generates one ormore analog beams from a subset of the analog beamformers 304 a, 304 b,304 c and 340 d.

At 1710, the hybrid beamformer generates, in the first cluster, one ormore hybrid beams from the analog beams in the first cluster, with eachhybrid beam generated by combining one or more analog beams in the firstcluster. For example, as described with respect to FIG. 14B, the hybridbeamformer 302 generates hybrid beams in the cluster 1420. As notedpreviously, a hybrid beam is a digital beam that is generated bycombining one or more analog beams in a cluster.

At 1712, the hybrid beam arranges the hybrid beams in the first clusterinto rows and columns. For example, the hybrid beamformer 302 arrangesthe hybrid beams in the cluster 1420 into one or more rows, e.g., rows1420 a, 1420 b, 1420 c, and one or more columns, e.g., columns 1430 a,1430 b and 1430 c. The hybrid beams are arranged into rows and columnssuch that the dimensions of each row and each column are withinpreselected limits that are selected to reduce the effect of side lobes,as described with respect to FIG. 14B.

At 1714, the hybrid beamformer selects another region of the pluralityof regions neighboring the preceding processed region. For example,after generating the cluster 1420 of hybrid beams, the hybrid beamformer302 selects the region neighboring the region covered by the cluster1420, as described with respect to FIG. 14C.

At 1716, the hybrid beamformer controls panels of feeds on thespacecraft to generate analog beams for a neighboring cluster in theneighboring region, each panel generating one or more analog beams inthe neighboring cluster. For example, the hybrid beamformer 302 controlsthe analog beamformers 304 a, 304 b, 304 c and 340 d to generate aplurality of analog beams, such as analog beams 1440 a, 1440 b and 1440c, among others, for the neighboring region, thereby forming the cluster1440.

In some implementations, the hybrid beamformer 302 generates one or moreanalog beams corresponding to the cluster 1440 from each analogbeamformer 304 a, 304 b, 304 c and 340 d. In other implementations, thehybrid beamformer 302 generates one or more of these analog beams from asubset of the analog beamformers 304 a, 304 b, 304 c and 340 d.

In some implementations, the one ore more analog beams generated in theneighboring cluster use one or more of different frequencies, time hopsor polarizations than the one or more analog beams generated in thefirst cluster, to avoid interference between adjacent clusters. This isthe case, for example, as described with respect to FIGS. 16A and 16B.

In some implementations, the one ore more analog beams generated in theneighboring cluster use the same frequency, time hop and polarizationsas the one or more analog beams generated in the first cluster, therebyreducing the negative impact of side lobes to be within an acceptablerange. This is the case, for example, as described with respect to FIG.16C.

At 1718, the hybrid beamformer generates, in the neighboring cluster,one or more hybrid beams from the analog beams in the neighboringcluster, with each hybrid beam generated by combining one or more analogbeams in the neighboring cluster. For example, as described with respectto FIG. 14D, the hybrid beamformer 302 generates hybrid beams in thecluster 1440.

At 1720, the hybrid beamformer arranges the hybrid beams in theneighboring cluster into rows and columns, where the rows and columnsare adjacent to rows and columns of hybrid beams in the precedingprocessed region. For example, the hybrid beamformer 302 arranges thehybrid beams in the cluster 1440 into rows and columns as shown withrespect to FIG. 14B. As in other clusters, the hybrid beams are arrangedinto rows and columns such that the dimensions of each row and eachcolumn are within preselected limits that are selected to reduce theeffect of side lobes.

At 1722, the hybrid beamformer checks whether every region in the targetarea is covered. For example, after generating the cluster 1420 ofhybrid beams, the hybrid beamformer 302 checks whether all the desiredregions in the target area have been covered by clusters of hybridbeams. Upon determining that the adjacent region (e.g., corresponding tocluster 1440) have not been covered, the hybrid beamformer 302 generatesthe cluster 1440 of digital beams as described above. Similarly, aftergenerating the cluster 1440 of hybrid beams (and after generating acluster for every desired region) the hybrid beamformer 302 checkswhether all the desired regions in the target area have been covered byclusters of hybrid beams.

If the hybrid beamformer determines that all regions have not yet beencovered, then the hybrid beamformer selects each uncovered region andgenerates a cluster for the selected region, as described with respectto 1714-1720. For example, after generating the cluster 1440, the hybridbeamformer 302 determines that a third region above the cluster 1420 isremaining. As such, the hybrid beamformer generates the cluster 1450 ofhybrid beams, as described with respect to FIG. 14E.

When the hybrid beamformer determines, at 1722, that all regions havebeen covered, then the process 1700 ends. Accordingly, in the abovemanner, the hybrid beamformer processing circuitry 302 providescommunications coverage to all desired regions in a target area byhybrid beamforming.

FIG. 18 illustrates an example 1800 of hybrid beamforming rain fademitigation. The example 1800 shows how gateways may be formed intovarious gateway clusters. For example, example 1800 shows GatewayClusters A-D, each with their own set of four gateways. A gatewaycluster may be a set of gateways for which analog beams may be combinedto form digital beams. For example, each of the four gateways in GatewayCluster A may have a separate analog beam between the gateway and thesatellite, and the analog beams may overlap and provide correspondingdigital beams.

The gateways in each cluster may be located geographically proximatefrom one another. For example, the gateways in each cluster may belocated within one hundred miles of one another. While four gateways areshown in each of the gateway clusters of FIG. 18, additional or fewergateways may be included in gateway clusters. For example, a firstgateway cluster may include two gateways, a second gateway cluster mayinclude four gateways, and a third gateway cluster may include eightgateways.

The gateway clusters may provide all the data capacity for customers.For example, a satellite may provide data to the Gateway Clusters A andB, and the Gateway Clusters A and B may then provide data to hundreds ofcustomers. Accordingly, ensuring that the Gateway Clusters have highdata capacity with a satellite may be important.

As discussed above, rain fade may interfere with transmissions between asatellite and terrestrial gateways. For example, a thunderstorm above aterrestrial gateway may temporarily interfere with transmissions betweenthe terrestrial gateway and the satellite. Certain types ofcommunications may be particularly sensitive to rain fade. For example,V-band or Improved Ka-Band may be essentially unusable with aterrestrial gateway while it is raining at the location of theterrestrial gateway.

As shown in FIG. 18, initially Gateway Clusters A and B may actively bein communication with a satellite to transfer data between the gatewaysof the Gateway Clusters A and B and the satellite. Gateway Clusters Cand D may be spare Gateway Clusters that may be activated to communicatewith the satellite as needed. For example, if Gateway Clusters A and Dboth experience high rain fade, Gateway Cluster A may cease being usedto communicate with the satellite and Gateway Cluster C may be usedinstead. Accordingly, sufficient data capacity to customers may bemaintained even when rain fade is present.

Selection of the gateway clusters to use may be complicated by the factthat each gateway within a gateway cluster may experience a differentamount of rain fade than another gateway within the same. For example, afirst gateway in a gateway cluster may experience rain fade thatattenuates signals between the satellite by −30 dBW and a second gatewayin the gateway cluster may experience rain fade that attenuates signalsbetween the satellite by −5 dBW, and for a different gateway cluster afirst gateway may experience rain fade that attenuates signals betweenthe satellite by −15 dBW and a second gateway in the gateway cluster mayexperience rain fade that attenuates signals between the satellite by−15 dBW. Accordingly, various factors may go into the selection of thegateway clusters to use based on rain fade.

FIG. 19 illustrates an example of a process 1900 for hybrid beamformingrain fade mitigation. In some implementations, the process 1900 isperformed by hybrid beamformer processing circuitry in a spacecraft,e.g., by the spacecraft hybrid beamformer processing circuitry 302,which includes one or more analog beamformer processors 304 a, 304 b,304 c and 304 d, and one or more digital beamformer processors such as306. As described previously, in some implementations, the spacecraft isan orbiting satellite, such as the satellite 105. Accordingly, thefollowing section describes the process 1900 with respect to thespacecraft hybrid beamformer processing circuitry 302. However, theprocess 1900 also can be performed by other processing circuitryconfigurations, and/or by other types of spacecraft or by a centraloperations center.

In some implementations, the hybrid beamformer processing circuitry,referred to henceforth interchangeably either as hybrid beamformer orprocessing circuitry, executes one or more instructions to perform theprocess 1900. These instructions are stored in memory, e.g., flashmemory, hard disk or some other suitable memory, which is coupled to thehybrid beamformer on board the spacecraft. Alternatively, in someimplementations, the instructions are sent to the hybrid beamformer onboard the spacecraft from the ground, e.g., through satellite gateway110 or 125.

The process 1900 starts at 1902, in which fade conditions are determinedfor each gateway in gateway clusters of a set of gateway clusters. Forexample, the satellite 105 may determine that there is no rain fade atany of the gateways for Gateway Clusters B and C, for Gateway Cluster Athe gateways are experiencing rain fade that attenuates signals betweenthe gateways and the satellites by −5 dBW, −30 dBW, −10 dBW, and −25dbW, respectively, and for Gateway Cluster D the gateways areexperiencing rain fade that attenuates signals between the gateways andthe satellites by −20 dBW, −30 dBW, −25 dBW, and −30 dbW, respectively.

In some implementations, determining fade conditions for each gateway ingateway clusters of a set of gateway clusters may include determining astrength of signals between each gateway and the satellite anddetermining the fade conditions from the strength of the signals. Forexample, the fade conditions for each gateway may be determined byhaving each gateway constantly sending signals that include a uniquetone or code word to the satellite 105. The satellite 105 may include awide-band antenna that detects each of the signals from the gateways,determines which signals come from which gateways based on the uniquetones or code words, and then determines the fade condition from thestrength of the signal. For example, the signals may all be transmittedat a known power and the satellite 105 may determine the relative fadebetween gateways based on the difference between the known power and thepower as detected by the wide-band antenna. For gateways that areactively providing data, the signal for determining the fade conditionsmay be transmitted in parallel with signals for data.

Additionally or alternatively, the satellite 105 may transmit wide bandbroadcasts that includes a tone or unique codeword that is received byall the gateways and each gateway may similarly determine an amount offade from the strength of the received signal. The gateways may thentransmit this information to a central operations center. Additionallyor alternatively, the satellite may transmit a tone or unique cord wordseparately across various beams.

In some implementations, gateways in each gateway cluster are operableto form an analog beam with a satellite where at least some of theanalog beams in each gateway cluster at least partially overlap and canbe combined to form a digital beam. For example, all four gateways mayhave corresponding analog beams where the analog beams may be combinedto form a single digital beam.

At 1904, a proper subset of the gateways clusters are selected based onthe fade conditions determined for each gateway. For example, thesatellite 105 or the central operations center may determine that thegateways in Gateway Clusters B and C are not experiencing fade and thegateways in Gateway Clusters A and D are and, in response, select theGateways Clusters B and C. In some implementations,

In some implementations, selecting a proper subset of the gatewayclusters based on the fade conditions determined for each gatewayincludes determining an aggregate data capacity for each of the gatewayclusters based on the fade conditions and selecting the gateway clusterswith aggregate data capacities that are the highest out of the set ofgateway clusters. For example, the satellite 105 or the centraloperations center may determine, based on the fade conditions, that theaggregate data capacity for Gateway Cluster B is highest followed byGateway Cluster C, then Gateway Cluster A, and then Gateway Cluster Dand, in response, select Gateway Clusters B and C as those GatewayClusters are the two Gateway Clusters with the highest aggregate datacapacities.

In some implementations, selecting a proper subset of the gatewayclusters based on the fade conditions determined for each gatewayincludes determining a number of gateways that satisfies a fadethreshold for each gateway cluster and selecting the gateway clusterswith the most number of gateways in the gateway cluster that satisfy thefade threshold. For example, the satellite 105 or the central operationscenter may have specified a fade threshold of −20 dBW, determine thatGateway Clusters B and C each have four gateways that have fadeconditions less than that threshold, determine that Gateway Cluster Ahas two gateways that have fade conditions less than that threshold,determine that Gateway Cluster D has no gateways less than thatthreshold, and, in response, select Gateway Clusters B and C as thosegateway clusters are the two gateways with the most gateways thatsatisfy the fade threshold.

In some implementations, selecting a proper subset of the gatewayclusters based on the fade conditions determined for each gatewayincludes not selecting a gateway cluster in the set of gateway clustersfor inclusion in the proper subset, where the gateway cluster that isnot selected is currently being used to transmit data with a satelliteand selecting a gateway cluster in the set of gateway clusters forinclusion in the proper subset, where the gateway cluster that isselected is not currently being used to transmit data with a satellite.For example, Gateways Clusters A and B may be currently transferringdata for customers between the satellite and gateways while GatewayClusters C and D are not, and the satellite 105 or central operationscenter may then select Gateway Clusters B and C, and not select GatewayClusters A and D.

While 1904 has been described with examples of selecting two gatewayclusters out of a set of four gateway clusters, other numbers ofgateways clusters may be used. For example, six out of a set of eightgateway clusters may be selected or seven out of a set of ten gatewayclusters selected.

At 1906, a beam plan is determined for the proper subset of the gatewayclusters. For example, the satellite 105 or the central operationscenter may determine a beam plan that includes beam coefficients foreach of the gateways in the selected gateway clusters. The beam plan mayspecify which gateway channels will be mapped to each beam.

At 1908, the beam plan is executed. For example, the satellite 105 maytransmit the beam plan to the gateways where the satellite 105 generatesthe beam plan, or where the central operations center generates the beamplan the center may transmit the beam plan to the gateways and to thesatellite 105. In some implementations, the beam plan may specify anactivation time. For example, the beam plan may specify that the beamplan be used for transmissions in one second from a current time.

In some implementations, multiple satellites may be used instead of asingle satellite 105.

The process 1900 is described above as being able to be performed by asatellite or a central operations center. Performing the process 1900 bythe satellite may have advantages over performing the process 1900 bythe central operations center as the central operations center may needto have separate communication links with each of the gateways toreceive information regarding fade and transmit beam plans to thegateways. Performing the process 1900 by the central operations centermay have advantages over performing the process 1900 by the centraloperations center as the satellite 105 may have more limited processingor power, and fixing problems on the satellite 105 may be moredifficult.

The disclosed and other examples can be implemented as one or morecomputer program products, i.e., one or more modules of computer programinstructions encoded on a computer readable medium for execution by, orto control the operation of, data processing apparatus. Theimplementations can include single or distributed processing ofalgorithms. The computer readable medium can be a machine-readablestorage device, a machine-readable storage substrate, a memory device,or a combination of one or more them. The term “data processingapparatus” encompasses all apparatus, devices, and machines forprocessing data, including by way of example a programmable processor, acomputer, or multiple processors or computers. The apparatus caninclude, in addition to hardware, code that creates an executionenvironment for the computer program in question, e.g., code thatconstitutes processor firmware, a protocol stack, a database managementsystem, an operating system, or a combination of one or more of them.

A system may encompass all apparatus, devices, and machines forprocessing data, including by way of example a programmable processor, acomputer, or multiple processors or computers. A system can include, inaddition to hardware, code that creates an execution environment for thecomputer program in question, e.g., code that constitutes processorfirmware, a protocol stack, a database management system, an operatingsystem, or a combination of one or more of them.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a standalone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed for execution on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communications network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random access memory or both. The essential elements of a computer caninclude a processor for performing instructions and one or more memorydevices for storing instructions and data. Generally, a computer canalso include, or be operatively coupled to receive data from or transferdata to, or both, one or more mass storage devices for storing data,e.g., magnetic, magneto optical disks, or optical disks. However, acomputer need not have such devices. Computer readable media suitablefor storing computer program instructions and data can include all formsof nonvolatile memory, media and memory devices, including by way ofexample semiconductor memory devices, e.g., EPROM, EEPROM, and flashmemory devices; magnetic disks, e.g., internal hard disks or removabledisks; magneto optical disks; and CD ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,special purpose logic circuitry.

While this document may describe many specifics, these should not beconstrued as limitations on the scope of an invention that is claimed orof what may be claimed, but rather as descriptions of features specificto particular embodiments. For example, a communications channel mayinclude the Web, where a user may interact with an interaction site viaa webpage generated dynamically according to the interaction flow. Asanother example, a communications channel may include a smart phoneapplication, where a user may interact with an interaction site bystarting a smart phone application, and the smart phone application thencontacts the interaction site and provides a communications interfacebetween the user and the interaction site. Certain features that aredescribed in this document in the context of separate embodiments canalso be implemented in combination in a single embodiment. Conversely,various features that are described in the context of a singleembodiment can also be implemented in multiple embodiments separately orin any suitable sub-combination. Moreover, although features may bedescribed above as acting in certain combinations and even initiallyclaimed as such, one or more features from a claimed combination in somecases can be excised from the combination, and the claimed combinationmay be directed to a sub-combination or a variation of asub-combination. Similarly, while operations are depicted in thedrawings in a particular order, this should not be understood asrequiring that such operations be performed in the particular ordershown or in sequential order, or that all illustrated operations beperformed, to achieve desirable results.

Only a few examples and implementations are disclosed. Variations,modifications, and enhancements to the described examples andimplementations and other implementations can be made based on what isdisclosed.

What is claimed is:
 1. A computer-implemented method comprising:determining fade conditions for one or more gateways in gateway clustersof a set of gateway clusters; selecting a proper subset of the gatewayclusters based on the fade conditions determined for the one or moregateways, wherein selecting the proper subset of the gateway clusterscomprises: deselecting a first gateway cluster of the set of gatewayclusters that is currently active in data transmission with a satellite,the first gateway cluster including a plurality of gateways, andselecting a second gateway cluster of the set of gateway clusters forinclusion in the proper subset, wherein the second gateway cluster iscurrently inactive for data transmission with the satellite, the secondgateway cluster including a plurality of gateways; determining a beamplan based on the proper subset of the gateway clusters; and executingthe beam plan.
 2. The method of claim 1, wherein the gateways in agateway cluster are operable to form an analog beam with a satellite,wherein at least some of the analog beams in a gateway cluster at leastpartially overlap and combine to form a digital beam.
 3. The method ofclaim 1, wherein selecting a proper subset of the gateway clusters basedon the fade conditions determined for the one or more gatewayscomprises: determining an aggregate data capacity for at least aplurality of the gateway clusters based on the fade conditions; andselecting the gateway clusters with aggregate data capacities that arethe highest out of the set of gateway clusters.
 4. The method of claim1, wherein selecting a proper subset of the gateway clusters based onthe fade conditions determined for each gateway comprises: determining,for each of at least a plurality of the gateway clusters, a number ofincluded gateways that satisfies a fade threshold; and selecting thegateway clusters with the most number of included gateways that satisfythe fade threshold.
 5. The method of claim 1, wherein determining fadeconditions for the one or more gateways in the gateway clusters of theset of gateway clusters comprises: determining a strength of signalsbetween each gateway of the one or more gateways and the satellite; anddetermining the fade conditions from the strength of the signals.
 6. Themethod of claim 1, wherein determining a beam plan based on the propersubset of the gateway clusters comprises: determining beamformingcoefficients for each of the gateways in the proper subset of thegateway clusters based on the gateways in the proper subset of thegateway clusters.
 7. The method of claim 1, wherein executing the beamplan comprises: providing the beam plan to the gateways in the propersubset of the gateway clusters from a satellite that is in communicationwith the set of gateway clusters.
 8. The method of claim 1, whereinselecting a proper subset of the gateway clusters based on the fadeconditions determined for the one or more gateways is performed by asatellite.
 9. The method of claim 1, wherein selecting a proper subsetof the gateway clusters based on the fade conditions determined for theone or more gateways is performed by a central operations center. 10.The method of claim 1, wherein the set of gateway clusters includes afirst plurality of active gateway clusters that are currentlycommunicating with the satellite, the first plurality including thefirst gateway cluster, and a second plurality of spare gateway clustersthat are not currently communicating with the satellite, the secondplurality including the second gateway cluster, and wherein the secondgateway cluster is selected as a replacement for the first gatewaycluster for communicating with the satellite.
 11. The method of claim 1,wherein determining fade conditions for the one or more gateways in thegateway clusters comprises, for a gateway cluster, controlling one ormore gateways in the cluster to transmit a signal to a satellite, thesignal transmitted at a known power and including a unique tone or codeword identifying the corresponding gateway, and wherein the methodfurther comprises: identifying, by the satellite, the gatewayscorresponding to received signals using the unique tones or code words;and determining, by the satellite, relative fades with the gateways bycomputing a difference between the known power and signal power detectedby the satellite.
 12. The method of claim 1, wherein determining fadeconditions for the one or more gateways in the gateway clusterscomprises, for a gateway cluster, controlling a satellite to transmit asignal to each of one or more gateways in the gateway cluster, thesignal transmitted at a known power and including a unique tone or codeword corresponding to the gateway, and wherein the method furthercomprises, for each of one or more gateways in a gateway cluster:determining a relative fade with the satellite by computing a thedifference between the known power and signal power detected by thegateway; and transmitting information about the relative fade to acentral operations center, the information including the unique tone orcode word corresponding to the gateway.
 13. A system comprising: aprocessor; and a non-transitory computer-readable medium storinginstructions executable by the processor and, when executed, configuredto cause the processor to perform operations comprising: determiningfade conditions for one or more gateways in gateway clusters of a set ofgateway clusters; selecting a proper subset of the gateway clustersbased on the fade conditions determined for the one or more gateways,wherein selecting the proper subset of the gateway clusters comprises:deselecting a first gateway cluster of the set of gateway clusters thatis currently active in data transmission with a satellite, the firstgateway cluster including a plurality of gateways, and selecting asecond gateway cluster of the set of gateway clusters for inclusion inthe proper subset, wherein the second gateway cluster is currentlyinactive for data transmission with the satellite, the second gatewaycluster including a plurality of gateways; determining a beam plan basedon the proper subset of the gateway clusters; and executing the beamplan.
 14. The system of claim 13, wherein the gateways in a gatewaycluster are operable to form an analog beam with a satellite, wherein atleast some of the analog beams in a gateway cluster at least partiallyoverlap and combine to form a digital beam.
 15. The system of claim 13,wherein selecting a proper subset of the gateway clusters based on thefade conditions determined for the one or more gateways comprises:determining an aggregate data capacity for at least a plurality of thegateway clusters based on the fade conditions; and selecting the gatewayclusters with aggregate data capacities that are the highest out of theset of gateway clusters.
 16. The system of claim 13, wherein selecting aproper subset of the gateway clusters based on the fade conditionsdetermined for each gateway comprises: determining, for each of at leasta plurality of the gateway clusters, a number of included gateways thatsatisfies a fade threshold; and selecting the gateway clusters with themost number of included gateways that satisfy the fade threshold. 17.The system of claim 13, wherein determining fade conditions for the oneor more gateways in the gateway clusters of the set of gateway clusterscomprises: determining a strength of signals between each gateway of theone or more gateways and the satellite; and determining the fadeconditions from the strength of the signals.
 18. The system of claim 13,wherein determining a beam plan based on the proper subset of thegateway clusters comprises: determining beamforming coefficients foreach of the gateways in the proper subset of the gateway clusters basedon the gateways in the proper subset of the gateway clusters.
 19. Thesystem of claim 13, wherein executing the beam plan comprises: providingthe beam plan to the gateways in the proper subset of the gatewayclusters from a satellite that is in communication with the set ofgateway clusters.
 20. The system of claim 13, wherein selecting a propersubset of the gateway clusters based on the fade conditions determinedfor the one or more gateways is performed by a satellite.
 21. The systemof claim 13, wherein the set of gateway clusters includes a firstplurality of active gateway clusters that are currently communicatingwith the satellite, the first plurality including the first gatewaycluster, and a second plurality of spare gateway clusters that are notcurrently communicating with the satellite, the second pluralityincluding the second gateway cluster, and wherein the second gatewaycluster is selected as a replacement for the first gateway cluster forcommunicating with the satellite.
 22. The system of claim 13, whereindetermining fade conditions for the one or more gateways in the gatewayclusters comprises, for a gateway cluster, controlling one or moregateways in the cluster to transmit a signal to a satellite, the signaltransmitted at a known power and including a unique tone or code wordidentifying the corresponding gateway, and wherein the operationsfurther comprise: identifying, by the satellite, the gatewayscorresponding to received signals using the unique tones or code words;and determining, by the satellite, relative fades with the gateways bycomputing a difference between the known power and signal power detectedby the satellite.
 23. The system of claim 13, wherein determining fadeconditions for the one or more gateways in the gateway clusterscomprises, for a gateway cluster, controlling a satellite to transmit asignal to each of one or more gateways in the gateway cluster, thesignal transmitted at a known power and including a unique tone or codeword corresponding to the gateway, and wherein the operations furthercomprise, for each of one or more gateways in a gateway cluster:determining a relative fade with the satellite by computing a thedifference between the known power and signal power detected by thegateway; and transmitting information about the relative fade to acentral operations center, the information including the unique tone orcode word corresponding to the gateway.
 24. A non-transitorycomputer-readable medium storing instructions executable by one or moreprocessors and, when executed, configured to cause the one or moreprocessors to perform operations comprising: determining fade conditionsfor one or more gateways in gateway clusters of a set of gatewayclusters; selecting a proper subset of the gateway clusters based on thefade conditions determined for the one or more gateways, whereinselecting the proper subset of the gateway clusters comprises:deselecting a first gateway cluster of the set of gateway clusters thatis currently active in data transmission with a satellite, the firstgateway cluster including a plurality of gateways, and selecting asecond gateway cluster of the set of gateway clusters for inclusion inthe proper subset, wherein the second gateway cluster is currentlyinactive for data transmission with the satellite, the second gatewaycluster including a plurality of gateways; determining a beam plan basedon the proper subset of the gateway clusters; and executing the beamplan.